UNIVERSITY  Or 

CALIFORNIA  COLLE:  -  ..- 

;   ;0"  • 

AUG    12    1974 

' 
IRVINE,  CAUrURWIA  92664 


JANUARY  1885. 


,HUMAN   OSTEOLOG-Y 

COMPRISING 

A  DESCRIPTION  OP  THE  BONES 

WITH  DELINEATIONS  OF  THE  ATTACHMENTS  OF  THE  MUSCLES, 

THE  GENERAL  AND  MICROSCOPIC  STRUCTURE  OF 

BONE  AND  ITS  DEVELOPMENT 


LUTHER  HOLDEN 

EX-PBESIDENT  AND  MEMBEB  OF  THE  COURT  OF  EXAMINEES  OF  THE  BOYAL  COLLEGE  OF 

SUBQEONS  OF  ENGLAND;    CONSULTING  8UBGEON  TO  SAINT  BABTHOL- 

OatEW'8  AND  THE  FOUNDLING  HOSPITALS. 

ASSISTED    BY 

JAMES  SHUTER,  F.R.C.S.  M.A.  M.B.  CANTAB. 

ASSISTANT  8UBGEON  TO  THE  BOTAL  FBEE  HOSPITAL ;  LATE  DEMONSTBATOB  OP  PHYSIOLOGY, 

AND  ASSISTANT  DEMONSTBATOB  OF  ANATOMY,  AT 

SAINT  BARTHOLOMEW'S  HOSPITAL. 


WITH  NUMEROUS  ILLUSTRATIONS 
SIXTH  EDITION. 


NEW  YORK 

WILLIAM  WOOD   &   COMPANY 
56  &  58  LAFAYETTE  PLACE 
1885. 


THE  PUBLISHERS 

PRINTING  AND  ELECTROTYPING  Co., 

39  AND  41  PARK  PLACE, 

NEW  YORK. 


PREFACE  TO  THE  FIFTH  EDITION. 


IN  preparing  the  present  Edition  the  Author  has  been  assisted  by 
Mr.  ALBAN  DOBAN,  late  Anatomical  Assistant  to  the  Museum  of  the 
Royal  College  of  Surgeons  of  England. 

In  revising  the  Attachments  of  Muscles,  note  has  been  taken  of 
the  highly  instructive  dissections, — made  by  Mr.  W.  PEARSON  in 
the  work-rooms  of  the  College, — which  are  now  in  the  Physiological 
Series  of  the  Museum. 

Most  of  the  Plates  have  been  re-drawn.  Numerous  woodcuts 
have  been  added,  in  illustration  of  the  Development  of  Bone — for 
which,  as  well  as  for  other  collateral  work,  the  author  is  indebted 
to  Mr.  JAMES  SHUTER,  Assistant  Demonstrator  of  Anatomy  at  St. 
Bartholomew's  Hospital. 

Grateful  acknowledgments  are  due  to  Professor  FLOWER, 
F.R.S.,  and  to  the  Demonstrators  of  St.  Bartholomew's  Hospital,  for 
valuable  suggestions  in  special  details. 

September  1878. 


PREFACE  TO  THE  SIXTH  EDITION. 


IN  THE  SIXTH  EDITION  a  few  brief  Notes  on  Comparative  Osteology 
have  been  added,  with  the  object  of  facilitating  the  intelligent 
study  of  the  human  skeleton ;  and  these  have  been  made  practically 
illustrative  by  reference  to  specimens  in  the  Museum  of  the  Royal 
College  of  Surgeons. 

Several  of  the  Plates  have  been  re-drawn. 

The  order  in  which  the  Bones  were  described  in  previous 
Editions  has  been  slightly  altered;  and  it  is  hoped  that  the  ar- 
rangement in  the  present  edition  will  be  found  more  systematic  and 
convenient. 

The  Author  has  been  assisted  by  Mr.  JAMES  SHUTEB,  late  De- 
monstrator of  Practical  Physiology,  and  Assistant  Demonstrator  of 
Anatomy,  at  St.  Bartholomew's  Hospital. 

January  1882, 


CONTENTS 


GENERAL  OBSERVATIONS  ON 
OF  BONE 


STRUCTURE 


MICROSCOPIC  STRUCTURE  OP  BONE     . 
STRUCTURE  OP  CARTILAGE 
DEVELOPMENT  OF  BONE 

BONES  OP  THE  SKULL 
Occipital  Bone 
Parietal  Bone 
Frontal  Bone 
Temporal  Bone 
Sphenoid  Bone 
Ethmoid  Bone 

BONES  OF  THE  FACE 

Superior  Maxillary  Bone  . 

Malar  Bone 

Nasal  Bone 

Lachrymal  Bone     . 

Palate  Bone 

Inferior  Spongy  or  Turbinated  Bone 

Vomer         .... 

Inferior  Maxillary  Bone    . 

THE  SKULL  AS  A  WHOLE 

Sutures         .... 
Skull-cap     . 

Base  of  the  Skull  as  seen  from  above 
Base  of  the  Skull  as  seen  from  below 


I.  to  IV. 


33 

.    V. 

38 

.    VI. 

41 

.    VII. 

47 

.  vm.,ix. 

56 

.     X.,  XI. 

64 

.    XI. 

68 

68 

.   xn. 

77 

.     XIII. 

78 

.    XVI. 

80 

.     XIII. 

81 

.    XIII.,  XIV. 

84 

.     XV. 

85 

.    XVI. 

86 

.    XVII. 

92 

92 

.   xvni. 

94 

.    XVIII. 

97 

.     XIX. 

99 

.     XX..  XXI 

vili                                                        CONTENTS. 

PAGE 

Temporal,  Zygomatic,  Spheno-maxillary 

Fossae       ..... 

103 

The  Orbits  .           . 

104 

Nasal  Fossae            .... 

107 

General  Observations  on  the  Skull 

109 

VERTEBRAL  COLUMN 

116 

SACRUM             ..... 

132  ) 

COCCYX                                                          , 

136  \ 

BONES  OF  THE  LOWER  EXTREMITY     . 

138 

Os  Innominatum    . 

188  -I 

Ilium           ..... 

139  1 

Pubes          .           .           .           .           . 

141 

Ischium       ..... 

143  J 

Pelvis  in  general     .... 

146 

Femur         ..... 

151 

Patella         

158" 

Tibia           

159 

Fibula         

163 

BONES  OF  THE  FOOT     .... 

167 

Astragalus   . 

168" 

Os  Calcis  or  Calcaneum     . 

171 

Scaphoid  Bone       .... 

173 

Cuboid  Bone           .... 

174 

Cuneiform  Bones    .... 

175 

Metatarsus              .... 

177 

Phalanges    ..... 

180 

Sesamoid  Bones     .... 

180. 

OBSERVATIONS  ON  THE  FOOT  AS  A  WHOLE 

181 

INTEROSSEUS  MUSCLES  OF  THE  FOOT  . 

185 

THE  THORAX     . 

186 

Sternum      ..... 

186 

Ribs             

189 

MUSCLES  OF  THE  BACK 

198"! 

Muscles  of  the  back  of  the  Neck  . 

200  1 

Muscles  in  the  front  of  the  Spine 

201  J 

XVI.,  XXII. 
XXII. 
XXIII.,  XXIV. 


XXV.  to  XXVII. 


XXVIII.,  XXIX. 


XXX.  to  XXXII. 


XXXIII.,  XXXIV. 


XXXVI.  to  XXXVIII. 


XXXIX.  to  XLI. 
XLI.  to  XLVII. 


CONTENTS. 


IX 


BONES  OF  THE  UPPER  EXTREMITY 
Clavicle 
Scapula 
Humerus 
Radius 
Ulna 

BONES  OF  THE  HAND    . 
Carpus 
Metacarpus  . 

BONES  OF  THE  FINGERS 
Sesamoid  Bones 
Interosseous  Muscles 

GENERAL  SURVEY  OF  THE  SKELETON 

OsHYOIDES 

THE  LARYNX     . 

THE  ANATOMY  OF  THE  EAR    . 

INDEX 


202 


216 
219 


.    224 
.     224 


.     235 
.    235 


237 


XL VIII. ,  XLIX. 

LI. 

LIL,  LIII. 


LIV.  to  LVI. 


.     241 

.     XXXVIII. 

,    243 

LVII. 

.    252 

.    LVIII.  to  LXI. 

.    271 

HUMAN  OSTEOLOGY. 


Importance  and  Interest  of  Osteology.— Whoever  would  become 
a  good  anatomist  and  a  skilful  surgeon  must  make  himself  master  of 
Human  Osteology.  It  must  be,  not  only  his  first,  but  his  principal  and 
constant  study.  He  cannot  understand  his  dissections  without  continually 
referring  to  the  skeleton.  Nor  can  he  fail  to  be  interested  from  the  first 
in  the  science,  if  in  studying  each  bone  he  will  compare  it  with  the  corre- 
sponding bone  in  his  own  body,  in  order  that  he  may  become  familiar 
with  what  he  can  feel  of  it  in  the  living  subject.  He  will  thus  see  in 
osteology,  not  death,  but  life.  In  discovering  and  reducing  the  simplest 
dislocation,  how  important  it  is  to  have  a  competent  knowledge  of  the  feel 
of  the  bony  parts  and  their  relations  to  one  another!  A  little  progress 
will  convince  him  that,  far  from  being  dry,  osteology  is  attractive,  not 
only  as  conducive  to  professional  success,  but  for  its  own  sake.  Under- 
taken in  a  right  spirit,  the  study  of  it  becomes,  with  many,  a  favorite  pur- 
suit, and  creates  a  natural  longing  to  know  something  of  the  skeleton  of 
the  lower  animals,  that  we  may  the  better  judge  of  the  advantageous  con- 
struction of  our  own;  for  it  is  only  by  comparison  that  we  can  judge. 
When  the  great  truth  unfolds  itself,  that  our  own  structure  appears  to  be 
but  a  modification  of  the  '  one  common  pattern'  upon  which  all  vertebrate 
animals  are  formed,  we  cannot  but  feel  with  the  philosophic  poet,  that — 

"Tis  the  sublime  of  man, 

Our  noontide  majesty,  to  know  ourselves 

Parts  and  proportions  of  a  wondrous  whole. 

COLERIDGE. 

Uses  of  the  Bones. — The  bones  form  the  framework  which  supports 
the  soft  parts  of  the  body.  All  the  bones,  either  separately  or  in  conjunc- 
tion with  others,  form  levers  upon  which  the  attached  muscles  act  and  give 


HUMAN    OSTEOLOGY. 

rise  to  our  various  movements.  Take  a  few  examples.  If  the  biceps  mus- 
cle contracts  the  forearm  becomes  flexed;  this  shows  that  the  radius  is  a 
lever  (see  Fig.  61).  It  will  likewise  be  seen  that  the  other  bones  are  levers, 
as  the  lower  jaw  in  opening  and  shutting  the  mouth;  the  skull  as  a  whole 
in  nodding  the  head;  the  vertebras  in  balancing  and  flexing  the  trunk;  the 
pelvis  as  a  whole  (see  Fig.  29) ;  the  ribs  when  raised  and  depressed  in  res- 
piration; the  clavicle  in  shrugging  or  depressing  the  shoulders;  the  scapula 
:and  the  humerus  in  raising  the  arm;  the  ulna  and  the  radius  in  flexing 
•or  extending  the  forearm;  the  carpus  and  metacarpus  as  a  whole  in  the 
movements  of  the  wrist  joint;  the  phalanges  in  the  actions  of  the  fingers. 
In  like  manner  the  bones  of  the  lower  extremities  are  levers,  which,  when 
acted  upon  by  the  various  muscles  attached  to  them,  give  rise  to  locomo- 
tion. 

The  bones  contribute  to  the  formation  of  the  joints,  which  admit  of 
more  or  less  movement,  depending  in  direction  and  extent  upon  the  shape 
of  the  articular  surfaces  and  the  attachments  of  the  muscles.  Besides 
this,  the  bones  of  the  head  and  trunk  lodge  and  protect  delicate  organs; 
thus,  in  the  skull  and  spinal  canal  we  find,  respectively,  the  brain  and 
spinal  cord;  in  the  orbits  are  the  eyes;  in  the  temporal  bone  are  the  inter- 
nal parts  of  the  ear;  and  in  the  bony  framework  of  the  chest  are  the  heart 
and  lungs,  which,  as  well  as  the  upper  abdominal  viscera,  it  protects. 

The  fact  that  the  long  bones  are  curved  in  their  long  axes  increases 
their  elasticity,  gives  them  some  amount  of  spring  similar  to  that  of  a  bow, 
and  helps  to  diminish  shocks. 

Composition  of  Bone. — Bone  is  composed  of  a  basis  of  animal  mat- 
ter impregnated  with  earthy  salts.  The  analysis  is  easily  made.  If  a 
bone  be  boiled  in  water  for  a  few  hours  it  loses  its  elasticity  and  its  animal 
matter.  The  animal  matter  is  found  in  solution  in  the  water  and  is  called 
jelly  or  '  gelatin/  The  residual  bone  is  white  and  brittle,  and  consists 
only  of  earthy  salts.  A  like  result  may  be  obtained  by  burning  or  calcin- 
ing the  bone:  it  first  becomes  black  from  the  charring  of  the  animal  mat- 
ter and  then  white,  the  animal  matter  having  been  completely  burnt  off 
and  nothing  left  but  the  '  earthy  salts/  If,  on  the  other  hand,  a  bone  be 
soaked  for  a  few  days  in  a  solution  of  hydrochloric  acid  (about  one  part  of 
the  dilute  acid  to  six  of  distilled  water),  it  loses  its  earthy  salts,  becomes 
soft,  and  may  be  bent  in  any  direction.  Bones  are  used  in  making  soup 
for  the  gelatin  they  yield  on  boiling.  Notwithstanding  their  antiquity, 
fossil  bones  are  found  to  contain  nearly  as  much  animal  matter  as  recent 


COMPOSITION    OF    BONE.  3 

bones.     Gimbernat  made  soup  from  the  gelatin  of  the  mastodon's  tooth, 
as  Dr.  Buckland  afterward  did  from  the  fossil  bones  of  the  hyaena. 

Animal  and  Earthy  Matter.— From  the  above  experiments  bone 
is  found  to  contain  about  one-third  of  animal  matter,  the  rest  being  earthy 
salts,  i.e.  about  33  of  animal  matter  and  67  of  earthy  salts  in  a  hundred 
parts.  Bones  of  children  are  softer,  more  elastic  and  less  likely  to  be 
broken  by  slight  injuries  than  those  of  the  aged.  This  is  due  to  the  spongi- 
ness  and  great  vascularity  of  children's  bones,  as  well  as  to  the  fact  that  in 
them  the  shafts  of  the  bones  are  united  to  the  epiphyses  by  a  layer  of  car- 
lilage.  Bone  when  pure,  i.e.  when  entirely  divested  of  fat  or  marrow  and 
blood-vessels,  is  probably  a  definite  compound  of  constantly  the  same  com- 
position, whether  it  be  from  a  child  or  from  an  old  person,  but  it  varies 
in  compactness  and  arrangement,  and  on  these  variations  the  differences 
in  the  strength  and  elasticity  of  bones  depend. ' 

The  following  is  a  percentage  analysis  of  adult  human  bone:—2 

Animal  matter 33.30 

Tribasic  phosphate  of  calcium       .        .     51  -04 
Carbonate  of  calcium,  Ca  C  0       .  11-30 


Earthy  salts  < 


Fluoride  of  calcium,  Ca  Fa   .        .        .2  -00 
Phosphate  of  magnesium      .  •      .  i-jg 

Soda  and  chloride  of  sodium  i  -20 


100-00 

Rickety  Bones.— In  the  disease  of  early  life  called  'rickets/  in 
which  the  bones  grow  bent  and  distorted,  from  deficiency  of  earthy  mat- 
ter, the  proportions  of  animal  and  earthy  matter  have  been  found  to  be—' 

Animal  matter 79.75  per  cent. 

Earthy  matter 20.25       " 

Of  all  animals,  the  bones  of  birds  (especially  of  the  predaceous  kind) 
contain  the  largest  proportion  of  earthy  matter.  Hence  their  great  com- 
pactness and  white  color.  The  bones  of  mammalia  come  next;  then  those 
of  reptiles;  and  last  of  all  those  of  fishes. 

As  in  the  birds  of  prey,  so  in  the  carnivora,  the  bones  have  a  hard  and 

1  Dr.  Stark,  'Edin.  Med.  and  Surg.  Jour.,'  April  1845;  Nelaton,  'Elements  de 
Pathologic,'  vol.  i.  p.  636. 

*  Berzelius's  '  Analysis  of  Bone. ' 

3  Dr.  Bostock's  'Analysis  of  Rickety  Bones.' 


4  HUMAN    OSTEOLOGY. 

compact  structure.  The  tympanic  bone  of  the  whale  is  extremely  hard; 
but  the  skeleton  most  remarkable  for  hardness  and  weight  is  that  of  the 
manatee,  which  may  be  seen  in  the  Osteological  Series  of  the  Eoyal  Col- 
lege of  Surgeons  of  England.  When  the  late  articulator  to  the  College 
was  taken  to  task  for  having  charged  the  enormous  sum  of  £15  (instead 
of  about  £5)  for  articulating  the  manatee,  he  pleaded,  in  justification, 
that  the  bones  were  so  hard  that  it  had  taken  him  unusual  labor  to  put 
them  together,  and  had  spoilt  many  of  his  tools.  The  truth  of  this  asser- 
tion is  at  once  clear  to  any  one  who  takes  in  his  hand  the  weighty  rib  of  a 
manatee.  (See  sections  of  ribs,  No.  2,653).* 

Phosphate  of  Lime:  its  Importance. — Of  the  earthy  ingredients 
of  bone  the  phosphate  of  lime  holds  by  far  the  first  rank;  hence  it  is  com- 
monly called  '  bone  earth/  Adult  bone  contains  51  per  cent,  of  it,  and 
about  11  per  cent,  of  the  carbonate  of  lime.  Carbonate  of  lime  is  the 
principal  ingredient  in  the  hardening  of  shells.  The  phosphate  of  lime 
forms  a  harder  compound  with  animal  matter  than  the  carbonate.  What 
can  be  harder  than  the  enamel  of  the  teeth?  And  this  consists  of  a  very 
large  proportion  of  phosphate  of  lime  combined  with  animal  matter. 
There  is  only  2  per  cent,  of  animal  matter  in  the  enamel,  and  of  the  re- 
maining 98  parts,  88J-  consist  of  phosphate  of  lime. 

Phosphate  of  lime  enters  not  only  as  the  principal  earthy  ingredient 
into  the  composition  of  bone,  but  is  contained,  more  or  less,  in  nearly  all 
the  tissues  of  the  body.  Of  all  inorganic  materials  it  appears  to  be  the 
most  essential  both  for  vegetable  and  animal  life.  Therefore  it  is  not  only 
a  most  important  article  of  diet,  but  a  necessary  manure.  '  Those  parts  of 
plants  which  experience  has  taught  us  to  be  the  most  nutritious,  contain 
the  largest  proportion  of.  the  phosphates — such  as  bread-corn,  peas,  beans, 
and  lentils/  *  It  has  been  ascertained  by  experiment,  that  if  animals  have 
their  entire  supply  of  phosphate  of  lime  cut  off,  after  some  weeks  of 
illness,  they  are  attacked  with  diarrhoea,  which  soon  kills  them.  Their 
bones  are  found  to  be  very  soft;  and  it  is  not  unlikely  that  the  phosphates 
are  absorbed  from  their  bones  and  supplied  to  other  structures,  such  as 
the  nerves  and  muscles. 

It  is  the  quantity  of  phosphate  of  lime  in  the  bones  which  makes  them 
so  valuable  as  manure.  The  bones  are  boiled  to  obtain  the  gelatin  or 

*  Throughout  the  work  the  numbers  refer  to  specimens  in  the  Osteological  Series 
in  the  Museum  of  the  Royal  College  of  Surgeons  of  England,  unless  otherwise  stated. 
4  Liebig's  'Letters  on  Chemistry,'  p.  522. 


PKOPEKTLES    OF    BONE.  5 

glue;  afterward  they  are  crushed  in  a  mill,  and,  as  *  bone  dust/  form  an 
extensive  article  of  commerce. 

Strength  of  Bone. — The  strength  of  bone,  contrasted  with  other 
substances,  is  remarkable.  The  following  materials  stand  in  point  of 
strength  to  each  other  thus: — 

Fine  freestone,  as 1  '0 

Lead 6-5 

Elm  and  ash 8-5 

Box,  yew,  oak 11-0 

Bone     . 22-0 

Hence  bone  is  twice  as  strong  as  oak.  A  cubic  inch  of  bone  will  support 
5,000  Ibs.  weight.6  Besides  this,  we  shall  presently  see  that  bone  is  so 
constructed  that  it  gives  great  strength  with  but  little  expenditure  of 
materials.  The  specific  gravity  of  bone  is  from  1*87  to  1'97. 

Elasticity  of  Bone. — In  consequence  of  the  animal  matter  they 
contain,  bones  possess  a  certain  amount  of  elasticity.  If  a  skull  be  thrown 
upon  the  ground,  it  will  rebound.  The  degree  of  elasticity  varies  in  dif- 
ferent bones,  according  to  their  form  and  texture.  The  clavicle,  for 
instance,  owing  to  its  curved  form,  is  remarkably  elastic — a  property 
which  enables  it  to  break  the  shock  of  a  fall  upon  the  hand.  If  one  end 
of  a  clavicle  be  placed  at  a  right  angle  against  a  hard  substance,  and  the 
other  end  struck  smartly  with  a  hammer,  the  bone  will  rebound  to  a  dis- 
tance of  nearly  two  feet.  The  ribs,  too,  are  exceedingly  elastic.  The 
Arab  children  are  said  to  make  excellent  bows  with  the  ribs  of  camels. 
Perhaps  the  best  instance  of  elasticity  in  bone  is  the  clavicle  (merry- 
thought) of  the  bird.  It  acts  as  a  spring,  and  restores  the  base  of  the 
wings  to  their  proper  position  after  the  action  of  the  muscles  of  flight. 
All  the  long  bones  are  more  or  less  curved,  which  gives  them  the  benefit 
of  elasticity. 

Classification  of  Bones. — Though  the  bones  present  every  variety 
of  form  and  size,  yet,  for  convenience  of  description,  anatomists  divide 
them  into  three  classes — 1.  The  long  and  round;  2.  The  broad  and  flat; 
3.  The  short  and  cubical,  or  irregular.  The  long  and  round  form  the  great 
levers  of  the  limbs,  and  are  moved  by  muscles.  The  broad  and  flat  are 
found  chiefly  in  the  skull  and  pelvis,  and  protect  the  viscera.  The  short 

5  Gregory's  'Mechanics,'  vol.  i.  c.  5. 


6  HUMAN     OSTEOLOGY. 

and  irregular  allow  more  limited  motion  combined  with  great  strength, 
as  the  bones  of  the  spine,  the  carpal  and  tarsal  bones. 

Nomenclature. — In  describing  the  different  parts  of  a  bone,  we  use 
terms — Latin,  Greek,  or  English — which  denote  either  the  form  of  the 
part,  or  its  fancied  resemblance  to  some  natural  object,  or  the  purpose  it 
serves.  We  soon  become  familiar  with  such  terms  as  *  eminences,'  '  depres- 
sions/ '  processes/  '  tuberosities/  e  spines/  c  foramina/  '  notches/  '  canals/ 
'  sinus/  '  fossae/  '  trochanters/  '  condyles/  etc.  Again,  there  are  parts  of 
bones  named  after  some  celebrated  anatomist,  who  first  described  them: 
for  instance,  the  '  aqueduct  of  Fallopius/  '  the  antrum  of  Highmore/  '  the 
fissure  of  Glaser/  the  '  canal  of  Vidius/  These  memorials  of  anatomists, 
though  interesting  to  historians,  are  rather  encumbering  to  anatomical 
nomenclature,  and  are  therefore  very  much  to  be  deprecated. 

Structure  of  Bone  :  Naked  Eye. — Let  us  examine,  first,  the  struct- 
ure of  bone,  as  it  can  be  seen  with  the  naked  eye;  afterward,  its  minute 
structure  with  the  microscope.  Lastly,  we  will  study  the  development 
and  growth  of  bone. 

The  best  way  to  obtain  a  rough  idea  of  the  structure  of  bone  is  to 
make  a  vertical  section  through  one  of  the  long  bones — say  the  femur — all 
the  way  down  (Plate  I.).  We  then  see  that  the  outer  part,  or  'wall/  of 
the  bone  is  compact  like  ivory;  the  interior  is  hollow,  forming  the  '  medul- 
lary canal/  or  cavity  containing  the  marrow.  The  ends,  which  expand  to 
form  the  joints,  are  composed  of  a  beautiful  network  of  plates  and  tubes 
of  bone,  forming  what  is  called  '  cancellous  or  spongy  tissue/  which  in 
the  recent  state  is  also  filled  with  marrow. 

Shaft  of  Bone  hollow. — What  are  the  advantages  of  bones  being 
hollow?  The  amount  of  material  being  the  same,  a  hollow  cylinder  is 

much  stronger  than  a  solid  one.  It  is 
proved'that  the  crushing  pressures  of  two 
cylinders  of  equal  weight  and  length,  of 
which  one  is  hollow  and  the  other  solid, 
are,  respectively,  as  the  diameters  of  their 
transverse  sections;  provided  always  that 
the  diameter  of  the  tube  be  within  cer- 
tain dimensions.  Thus,  let  a  b,  c  d  (Figs. 

1  and  2)  represent  the  sections  of  two  cylinders;  then  the  strength  of 
the  tube  c  d  is  to  that  of  the  solid  a  J  as  the  line  d  c  is  to  the  line  a  I. ' 
6  Bishop  '  On  Deformities',  1852,  p.  14. 


GENERAL    STRUCTURE    OF    BONE.  7 

In  some  animals  which  seldom  or  never  leave  the  water,  the  bones 
have  no  medullary  cavities,  but  are  completely  filled  by  cancellous  tissue. 
This  is  the  case  in  the  penguins  (Nos.  1138  to  1140),  the  whales,  and 
amphibia,  whose  solid  bones  appear  to  act  as  ballast. 

In  the  early  part  of  the  seventeenth  century,  Galileo  observed  in 
nature  a  variety  of  instances  in  which  the  strength  of  bodies  was  made 
very  great  consistently  with  lightness  by  the  arrangement  of  their  struct- 
ure. This  most  profound  philosopher,  when  accused  of  atheistical  opin- 
ions, and  interrogated  before  the  Inquisition  as  to  his  belief  in  a  Supreme 
Being,  picked  up  a  straw  from  the  floor  of  his  prison,  and  replied,  'If 
there  were  nothing  else  in  nature  to  teach  me  the  existence  of  a  Deity, 
even  this  straw  would  be  sufficient.' 

Air  Cells  in  Bone. — Strength  and  lightness  are  thus  combined  in 
the  economy  of  bones.  This  principle  is  carried  to  the  extreme  in  the 
bones  of  birds,  which  are  filled  with  air  instead  of  marrow.  There  is  a 
communication  between  the  lungs  and  the  cavities  in  the  bones  of  birds 
(Nos.  1107-8);  and  the  air  which  fills  the  bones  being  warm,  renders 
them  still  lighter.  The  extent  to  which  air  is  admitted  into  the  bones 
of  birds  is  generally  in  proportion  to  their  powers  of  flight.  The  ostrich 
(No.  1114),  which  never  flies,  has  air  only  in  the  bones  of  his  legs.  The 
great  beak  of  the  hornbill  forms  one  large  air  cell  (No.  1492);  even  the  thin 
columns  of  the  cancellous  tissue  in  the  interior  are  hollow  and  filled  with 
air.  In  this  bird,  as  well  as  in  the  toucan,  every  bone  of  the  skeleton,  down 
to  the  little  bones  of  the  claws,  is  filled  with  air.  In  the  little  '  apteryx* 
of  New  Zealand,  which  has  no  available  wings,  and  in  the  penguin,  which 
rarely  leaves  the  water,  no  bones  of  the  skeleton  except  those  of  the  skull 
receive  air.  In  the  bones  of  the  chick  there  are  no  medullary  cavities;  as 
the  bird  grows  its  bones  become  hollowed  out,  and  filled  with  marrow, 
which  is  subsequently,  in  the  mature  bird,  removed  and  replaced  by  warm 
air.  In  mammalia  there  are  no  air  cells  except  in  the  bones  of  the  head. 
There  are  large  air  cells  (sinuses)  in  the  frontal,  sphenoid,  ethmoid, 
palate,  maxillary  and  mastoid  bones  in  man. 

Bone  divisible  into  Layers. — Although  the  compact  tissue  of  bone 
seems  hard  and  solid  as  stone,  yet  it  is  made  up  of  layers  placed  so  close 
together,  that  there  is  no  apparent  interval  between  them.  Toward  the 
articular  ends  (Plate  I.  Fig.  3),  the  layers  gradually  separate  to  form  the 
cancellous  tissue,  and  the  compact  tissue  becomes  thinner  in  proportion. 
In  bones  long  weather-beaten  in  a  churchyard,  these  layers  may  be  peeled 


8  HUMAN     OSTEOLOGY. 

off  one  after  another;  or  if  the  earthy  matter  be  removed  by  acid,  the 
animal  matter  admits  of  being  stripped  off  like  so  many  leaves.  It  is 
essential  to  bear  in  mind  this  lamellar  structure 
of  bone,  because  it  explains  what  is  observed  in 
cases  of  inflammation  of  bone — namely,  that  the 
enlargement  of  the  blood-vessels  together  with  the 
inflammatory  deposit  separates  the  layers  from  each 
other,  and  thus  causes  the  bone  to  expand  and  be 
perceptibly  increased  in  diameter,  as  seen  in  the 
adjoining  wood-cut  (Fig.  3),  taken  from  a  prepara- 
tion in  the  museum  of  St.  Bartholomew's  Hospital. 
Cancellous  Tissue:  Arrangement. — The  cancellous  tissue  occu- 
pies the  interior  of  bones,  and  chiefly  the  articular  ends.  It  is  formed  by 
the  separation  of  the  component  layers  of  the  bone,  and  these  are  con- 
nected by  cross  plates  and  fine  tubes,  which  form  a  kind  of  lattice-work 
with  a  most  delicate  and  elegant  arrangement.  The  cancellous  archi- 
tecture of  bones  is  arranged  upon  this  principle: — its  columns  always  run 
along  the  lines  of  greatest  pressure,  thus  combining  the  greatest  strength 
and  elasticity  with  lightness.  A  beautifui  example  of  this  is  seen  in  the 
section  of  the  cancellous  tissue  of  the  thigh-bone  (Plate  I.).  At  the  lower 
part,  toward  the  knee,  the  layers  run  vertically — that  is,  in  the  direction 
of  the  axis  of  the  shaft,  this  being  the  line  of  pressure  when  the  body  is 
erect.  But  in  the  neck  of  the  thigh-bone  the  layers  are  arranged  in  de- 
cussating curves  like  Gothic  arches,  one  within  the  other,  and  sustain 
with  the  greatest  mechanical  advantage  the  weight  transmitted  on  to  the 
heads  of  the  thigh-bones.  (Norm.  Hum.  Ost.,  Nos.  211  to  222). 

Cancellous  Tissue:  Properties. — Though  so  light  and  spongy,  the 
cancellous  tissue  is  able  to  support  a  great  weight  without  giving  way. 
"We  may  form  some  idea  of  its  strength  from  the  following  experiment:7 
— A  cubic  inch  of  cancellous  texture  was  taken  from  the  lower  end  of  the 
femur,  and  placed  with  its  principal  layers  upright.  Four  cwt.  was  then 
placed  upon  it,  but  it  did  not  give  way  in  the  least.  Six  cwt.  made  it 
sink  half  an  inch.  Yet  the  cubic  inch  of  bone  itself  did  not  weigh  more 
than  54  grains.  Not  only  is  cancellous  tissue  strong  as  well  as  light,  but 
it  possesses  another  advantage — that  of  diminishing  shocks.  When  a  ball 
of  ivory  strikes  another,  as  in  the  game  of  billiards,  the  whole  force  of  the 
shock  is  transmitted  from  one  to  the  other;  but  let  a  ball  made  of  the 
1  '  Outlines  of  Osteology, '  p.  368.  T.  Ward. 


GENERAL    STRUCTURE    OF    BONE.  9 

cancellous  tissue  be  interposed,  and  then  see  how  the  shock  will  be  broken. 
This  property  of  diminishing  shocks  is  of  course  greater  when  the  bone  is 
in  its  natural  state  and  filled  with  marrow. 

The  spaces  formed  by  the  cancellous  tissue  vary  in  size  and  shape,  but 
freely  communicate  with  each  other,  and  with  the  holes  on  the  surface 
of  the  bones.  This  is  easily  proved  by  boring  a  hole  at  one  end  of  a  bone, 
and  pouring  mercury  into  it: — we  shall  find  that  the  mercury  will  run  out 
freely  through  the  natural  holes  at  the  other  end. 

*  Marrow,  Yellow. — The  interior  of  the  shaft  of  a  long  bone  is  filled 
with  yellow  marrow;  a  substance  composed  almost  entirely  of  fat  (96  per 
cent.);  that  is,  in  bones  that  are  healthy.  Like  all  other  fat,  it  is  re- 
moved in  cases  of  great  emaciation — in  general  dropsy,  for  instance;  and 
its  place  is  supplied  by  an  albuminous  fluid.  Hence  the  bones  of  a  drop- 
sical subject  are  always  the  least  greasy,  and  the  best  adapted  for  skeletons. 

Marrow,  Red. — The  cancellous  tissue  of  the  articular  ends  of  long 
bones,  and  of  the  bodies  of  the  vertebrae,  the  sternum,  the  ribs,  and  the 
bones  of  the  cranium,  contain  another  kind  of  marrow  of  a  red  color. 
This  red  marrow  differs  from  the  yellow,  in  that  it  contains  little  or  no 
fat — not  more  than  1  per  cent.  It  consists  of  75  per  cent,  of  water  and 
25  per  cent,  of  solid  matters,  chiefly  albumen.  It  is  this  kind  of  marrow 
which  is  found  in  all  the  bones  of  the  foetus,  and  in  infants.  Hence  it 
is  sometimes  called  foetal  marrow.  Examined  with  a  high  magnifying 
power,  it  is  found  to  contain  a  number  of  oval,  many-nucleated  cells 
(Plate  IV.  Fig.  9).  Cells  of  this  form  are  found  in  most  rapidly  growing 
tumors  and  are  called  '  myeloid '  cells.  They  form  the  greater  part  of  the 
so-called  myeloid  tumors.8 

Blood  supply  of  Bones. — At  the  articular  ends  of  any  long  bone,  or 
on  the  body  of  a  vertebra,  we  observe  a  number  of  holes.  Near  the  lower 
end  of  the  thigh-bone  we  might  soon  count  as  many  as  200  or  more. 
What  are  these  holes?  The  smaller  transmit  the  articular  arteries  which 
nourish  the  vascular  cancellous  tissue.  The  larger  contain  veins  which 
run  by  themselves.  These  veins  of  the  cancellous  tissue  are  large  and  nu- 
merous. They  traverse  and  ramify  through  this  tissue  in  various  direc- 
tions in  special  canals  with  thin  walls  of  bone.  They  are  well  seen  in  a 
section  through  the  body  of  a  vertebra  (Plate  XXV.  Fig.  7),  also  in  the 
cancellous  tissue  (termed  '  diploe ')  of  the  cranial  bones.  From  a  surgical 
point  of  view  these  '  diploic'  veins  are  interesting,  on  account  of  their  lia- 
8  'Lectures  011  Surgical  Pathology.'  Sir  J.  Paget,  F.R.S. 


10  HUMAN    OSTEOLOGY. 

bility  to  inflame  after  severe  injuries  of  the  head:  such  inflammation  may 
lead  to  suppuration  in  the  diploe,  which  is  often  fatal.  The  adjoining 
figure  (4)  shows  the  large  venous  canals  in  the  '  diploe '  of  the  skull-cap. 
Again,  on  the  outside  of  the  shaft  of  a  long  bone  there  are  a  number 
of  minute  grooves,  which  run  for  the  most  part  parallel  to  the  shaft,  and 
lodge  blood-vessels.  At  the  bottom  of  these  grooves  lie  a  multitude  of 


4.—  Veins  in  the  Diploe  of  the  Skull. 


still  more  minute  holes,  barely  visible  to  the  naked  eye,  but  easily  seen 
through  a  small  pocket-lens.  These  holes  transmit  the  blood-vessels  from 
the  '  periosteum/  or  membrane  covering  the  bone,  to  the  compact  tissue. 

Artery  of  the  Marrow.  —  The  marrow  in  the  interior  of  the  bone  is 
supplied  with  blood  by  the  '  medullary  artery/  This  artery  reaches  the 
marrow  through  a  very  distinct  canal  (canal  for  the  nutrient  artery  of  the 
medulla),  which  runs  obliquely  through  the  shaft,  near  its  middle.  In 
a  long  bone  like  the  femur  there  are  generally  two  of  these,  situated  at  the 
back  part.  As  soon  as  the  artery  reaches  the  medullary  cavity,  it  divides 
into  two  branches,  an  ascending  and  a  descending,  which  ramify  in  and 
supply  the  marrow,  and  finally  communicate  with  the  f  articular  '  arteries 
already  described. 

Thus  the  several  parts  of  a  long  bone  are  supplied  with  blood  as  fol- 
lows: —  The  compact  wall  of  the  shaft  by  blood-vessels  from  the  perios- 
teum; the  marrow  in  the  interior  by  a  special  medullary  artery;  and  the 
cancellous  tissue  of  the  ends  by  the  articular  arteries.  The  blood-vessels 
of  these  several  parts  are  not  exclusive,  but  communicate  more  or  less  with 
each  other  when  the  parts  of  the  bone  have  united  with  the  shaft.  Hence 
they  readily  reciprocate  their  morbid  actions,  and  inflammation  arising  in 
the  one  part  may  spread  to  the  other.  Now,  although  these  three  orders 


GENERAL    STRUCTURE    OF    BONE. 


11 


FIG.  5.— Blood-Vessels  of  Perios- 
teum. 


of  blood-vessels  do  communicate  in  the  bone,  yet  we  cannot  be  surprised 
to  find  that  when  a  bone  is  broken  below  the  canal  for  the  nutrient  artery 
of  the  marrow,  the  lower  fragment,  being  deprived  of  part  of  its  supply  of 
blood,  in  some  cases  becomes  atrophied  and  thinner.' 

Periosteum  :  its  use. — A  fibrous  membrane,  termed  the  periosteum, 
invests  the  bones  everywhere  except  at  the  insertion  of  strong  tendons, 
and  where  covered  with  cartilage.  This  perios- 
teum consists  of  two  layers,  an  external  one, 
tough  and  fibrous,  and  an  internal  one  (osteo- 
genetic),  soft  and  cellular,  in  which  the  blood- 
vessels break  up  into  minute  branches  before 
penetrating  the  pores  on  the  surface  of  the 
bones.  The  adjoining  figure  shows  the  arrange- 
ment of  the  blood-vessels  of  the  periosteum. 
The  periosteum  likewise  provides  each  of  the 
vessels  entering  the  bone  with  a  fibrous  cover- 
ing. It  assists  in  the  formation  of  bone,  and 
afterward  in  its  nutrition.  If,  therefore,  the 
periosteum  be  torn  from  the  surface  of  a  bone, 
there  is  a  risk  that  a  layer  of  the  subjacent  bone  will  lose  its  vitality  and 
be  cast  off. 

Medullary  Membrane. — The  medullary  canal  and  the  cells  (marrow 
spaces)  of  the  cancellous  tissue  are  lined  by  an  extremely  delicate  mem- 
brane, termed  the  '  endosteum.'  It  is  much  more  delicate  than  the  perios- 
teum; nevertheless,  it  supports  the  marrow,  and  provides  a  stratum  for  the 
subdivisions  of  the  medullary  artery,  before  they  penetrate  the  contiguous 
bone. 

Nerves  in  Bone. — Periosteum  and  bone  unquestionably  possess 
nerves.  This  is  proved  by  absolute  demonstration,  and  by  disease.  Nerves 
may  be  traced  into  some  of  the  minute  foramina  on  the  shaft  of  a  long 
bone,  and  into  the  articular  ends.  A  nerve  also  enters  the  medullary 
canal  with  the  nutrient  artery  of  the  medulla,  and  divides  like  the  artery 
into  an  ascending  and  a  descending  branch.  Of  all  the  bones,  the  tibia 
presents  the  largest  canal  for  the  nutrient  artery  of  the  marrow;  in  this 
bone  also  it  is  easy  to  trace  the  entrance  of  the  nerve  with  the  artery. 
Though  bone  in  health  has  but  little  feeling,  when  diseased  it  becomes 
highly  sensitive.  There  is  such  a  thing  as  '  neuralgia '  of  bone.  Every 
•  Curling,  '  Medico-Chir.  Trans. '  vol.  xx. 


12  HUMAN   OSTEOLOGY. 

surgeon  must  have  witnessed  how  sensitive  are  granulations  from  bone. 
Indeed,  it  is  probable  that  the  severe  pain  attendant  on  the  ulceration  of 
articular  cartilage  is  occasioned  by  the  pressure  of  the  cartilage  on  the  bone 
granulations  beneath  it. 

Lymphatics  of  Bone.— The  lymphatics  of  bone  have  been  actually 
demonstrated  by  injecting  the  lymphatics  of  the  body  of  a  vertebra.10  It 
has  been  recently  proved  by  injections  that  the  blood-vessels  of  Haversian 
canals  are  surrounded  by  perivascular  lymphatic  vessels.11  This  accounts 
for  the  fact  that  ivory  pegs  introduced  into  bones,  for  the  purpose  of 
consolidating  ununited  fractures,  are  in  some  instances  absorbed. 

MICKOSCOPIC  STRUCTURE  OF  BOKE. 

This  is  a  most  interesting  and  instructive  study.  It  reveals  to  us  that 
bones  are  as  minutely  provided  with  blood-vessels  and  nerves  as  the  softer 
parts  of  the  body.  Being  as  fully  organized  as  other  parts,  we  cannot 
wonder  that  they  are  subject  tolike  diseases.  We  have  to  investigate  how 
the  bones  are  formed  in  early  life,  how  they  grow  to  maturity,  how  their 
health  is  maintained,  how  their  injuries  are  repaired.  Would  anyone, 
looking  at  a  solid  bone,  expect  to  find  that  even  its  hardest  parts  are  tun- 
nelled out  by  a  network  of  minute  canals  containing  blood-vessels;  and 
that  from  these  canals  other  tubes,  infinitely  more  minute,  and  connected 
with  a  series  of  reservoirs,  radiate  in  all  directions  and  convey  nutritious 
fluids? 

General  Idea :  Haversian  Canals. — Let  us  first  get  a  general  idea 
of  the  microscopic  structure  of  bone,  and  go  into  details  afterward.  If 
a  transverse  section  from  the  shaft  of  a  long  bone  be  ground  extremely 
thin,  and  examined  with  a  power  of  about  20  diameters  (Plate  II.  Fig.  5), 
we  see  a  number  of  holes,  with  dark  spots  grouped  around  them,  in  a 
series  of  tolerably  concentric  circles.  These  holes  are  sections  of  the 
canals  (termed  'Haversian')111  which  transmit  blood-vessels  into  the  sub- 
stance of  the  bone.  The  dark  spots  are  minute  reservoirs,  called  '  lacunae/ 
They  look  like  solid  bodies,  but  they  are  cavities  and  are  occupied  during 
life  by  soft  '  bone  corpuscles/  concerning  which  more  will  be  said  here- 
after. Different  parts  of  the  section  show  that  the  Haversian  canals  vary 

10  Cruikshank,  'Anatomy  of  the  Absorbent  Vessels/  1790,  p.  198. 

11  Budge,  '  Archivf.  Microso.  Anatomic,'  bd.  13. 

12  Dr.  Clopton  Havers,  an  English  physician  of  the  seventeenth  century,  was  the 
first  to  describe  these  canals. 


Bfcl. 


Fibre-  cartilage. 


m     m 


' 


Hyaline  cartilage. 
BONE. 


' 

Longitudinal  section  of 
Haversian  canals 


Transverse  section  of 
Hawersian  ca.na.ls. 


f/r   /  f/A  ^      7 
Lacunae  and  Car.alicali  Ki^ily  magnified 


lOOdia' 


:ife§B8:: 


•^<'••' 
^SK' 

wi^iir, 

Hawerstan  systems. 


MICROSCOPIC    STRUCTURE    OF    BONE.  13 

considerably  in  size  and  shape.  They  are  generally  round  or  oval.  Those 
nearest  to  the  circumference  of  the  bone  are  very  small;  but  toward  the 
medullary  cavity  they  are  seen  to  be  larger,  and  at  last  open  out  into  the 
cells  of  the  cancellous  texture. 

Haversian  Lamellae. — The  same  section  examined  with  a  higher 
power  (Plate  II.  Fig.  7)  shows  that  the  Haversian  canals  are  surrounded 
by  a  series  of  concentric  lines,  resembling  the  transverse  section  of  the 
branch  of  a  tree.  These  lines  are  termed  the  'lamellae/  They  are  so 
many  layers  or  rings  of  bone  that  have  been  developed  within  the  Haver- 
sian canal.  Even  the  smallest  Haversian  canal  was,  when  originally 
formed,  a  much  wider  space,  and  circumscribed  by  only  a  single  layer  of 
bone;  but  in  process  of  growth  the  canal  becomes  gradually  contracted 
by  the  deposit  of  successive  layers  of  bone.  The  dark  spots,  before  al- 
luded to  as  the  '  lacunae/  are  situated  between  the  lamellae;  under  a  higher 
magnifying  power  (Plate  II.  Fig.  6),  they  look  like  insects.  The  central 
part  or  the  lacuna,  representing  the  body  of  the  insect,  is  hollow,  and  the 
dark  filaments  which  run  out  from  it,  representing  the  legs,  are  minute 
tubes  termed  'canaliculi/  These  are  exceedingly  numerous,  and  radiate 
from  all  parts  of  the  *  lacuna/  through  the  lamellae.  Now,  since  the  ca- 
naliculi of  one  circle  of  lacunae  communicate  most  freely  with  those  of  the 
next  circle,  and  the  canaliculi  nearest  to  the  Haversian  canal  open  directly 
into  it,  it  follows  that  by  means  of  this  system  of  radiating  tubes  a  com- 
plete communication  is  established  between  the  Haversian  canal  in  the 
centre,  and  the  successive  circles  of  bone  which  surround  it.  The  nutri- 
ent material  of  the  bone  proceeds  from  the  perivascular  lymphatics  in  the 
central  canal,  and  is  transmitted  through  the  canaliculi  from  one  lacuna 
to  another. 

Haversian  System. — Every  Haversian  canal  taken  in  conjunction 
with  its  concentric  layers  of  bone,  lacunae,  and  canaliculi,  is  termed  an 
'  Haversian  system/  (Plate  II.  Fig.  7.) 

Almost  all  the  compact  substance  of  bone  is  made  up  of  a  multitude 
of  these  '  Haversian  systems/  Each  system  is,  to  a  certain  extent,  inde- 
pendent of  its  neighbor,  since  the  lacunae  of  one  system  communicate  very 
sparingly  with  those  of  another.  In  consequence  of  this  isolation,  we 
sometimes  find,  in  favorable  sections,  that  each  system  is  more  or  less  cir- 
cumscribed by  a  tolerably  distinct  white  line,  which  is  transparent  bone 
with  but  few  canaliculi. 

Haversian  Interspaces. — As  the  Haversian  systems  are  for  the  most 


14  HUMAN    OSTEOLOGY. 

part  circular,  and  arranged  like  sticks  in  a  faggot,  it  is  clear  they  cannot 
touch  each  other  in  all  parts  of  their  circumference;  so  that  here  and  there 
triangular  portions  of  bone  fill  up  the  gaps  between  them.  Such  portions 
are  termed  '  Haversian  interspaces.'  (Plate  II.  Fig.  7).  These  'outly- 
ing '  portions  of  bone  are  also  provided  with  lacunae  and  canaliculi,  and 
they  derive  their  nourishment  from  the  surrounding  Haversian  systems, 
of  which  they  are  dependencies. 

The  section  we  have  hitherto  been  examining  was  a  transverse  one. 
"We  must  now  make  an  equally  thin  section  in  the  longitudinal  direction 
of  the  shaft,  and  we  then  have  quite  a  different  appearance.  (Plate  II. 
Fig.  4.)  We  cut  in  the  course  of  the  Haversian  canals,  not  across  them; 
and  we  find  that,  as  a  general  rule,  they  run  parallel  to  the  surface  of  the 
bone  (no  matter  whether  long  or  fiat),  and  that  they  communicate  very 
frequently  by  transverse  or  more  or  less  oblique  canals.  If  the  section  be 
large  enough  to  include  the  Haversian  canals  near  the  circumference,  we 
find  that  many  open  on  the  outer  surface  and  admit  blood-vessels  from 
the  periosteum;  others,  again,  open  into  the  medullary  canal,  and  admit 
blood-vessels  from  the  interior.  In  this  way  the  Haversi%n  canals  permeate 
the  compact  substance  of  the  bone,  and  establish  a  free  communication 
between  the  blood-vessels  of  the  periosteum  and  those  of  the  medulla. 
These  canals  may,  in  fact,  be  regarded  as  so  many  multiplications  of  sur- 
face for  the  ramifications  of  blood-vessels,  whereby  every  part  of  the  bone 
substance  is  brought  within  the  range  of  nutrition. 

In  this  longitudinal  section,  the  lamellae,  instead  of  being  arranged 
concentrically,  are  seen  running  in  lines  parallel  with  the  Haversian 
canals  to  which  they  belong. 

Bone  Tissue. — At  this  stage  of  the  investigation,  a  question  naturally 
arises — Where  is  the  earthy  material,  the  phosphate  and  carbonate  of  lime? 
To  see  this,  the  transverse  section  must  be  magnified  about  1,200  diame- 
ters. (Plate  II.  Fig.  6.)  We  then  discover  that  the  earthy  ingredient 
consists  of  an  infinite  multitude  of  minute  osseous  granules,  which  are 
deposited  in  a  '  matrix '  or  bed  of  animal  matter.  This  mixture  of  earthy 
granules  and  animal  matter  is  called  'bone  tissue.'  It  occupies  all  the 
space  between  the  lacunae  and  their  canaliculi.  If  the  specimen  were 
steeped  for  a  time  in  dilute  hydrochloric  acid,  the  osseous  granules  would 
be  dissolved  out  of  it,  and  the  little  pits  in  the  matrix  in  which  the  gran- 
ules were  imbedded  would  become  apparent. 

So  far  we  have  acquired  a  general  notion  of  the  minute  structure 


MICROSCOPIC    STRUCTURE    OF    BONE.  15 

of  bone;  that  is  to  say,  of  the  '  Haversian  canals,'  the  '  lacunae/  and  their 
'  canaliculi/  the  '  lamellae/  and  the  '  osseous  granules/  "We  must  now 
speak  of  these  several  parts  a  little  more  in  detail;  and  first,  of  the 
Haversian  canals. 

Haversian  Canals. — As  said  before,  the  Haversian  canals  are  tun- 
nels in  the  compact  substance  of  the  bone,  which  contain  the  blood-ves- 
sels. Observe,  they  form  no  part  of  the  essential  structure  of  bone.  Wher- 
ever bone  is  so  thin  as  to  be  able  to  derive  its  nutrition  from  the  vascular 
membrane  covering  its  surface,  we  do  not  find  Haversian  canals  in  it,  nor 
does  it  require  any.  For  instance,  the  delicate  plates  of  bone  composing 
cancellous  tissue,  the  paper-like  bones  in  the  interior  of  the  nose,  have  no 
Haversian  canals  in  them;  but  they  have  plenty  of  lacunae,  which  send 
out  their  canaliculi  to  open  on  the  surface  and  imbibe  the  requisite  nutri- 
tion. Bone  so  thin  as  to  need  no  Haversian  canals  is  called '  non-vascular* 
bone.  Such  bone  lives  upon  the  blood  which  flows  through  the  minute 
vessels  of  its  periosteum.  Bone  has,  therefore,  like  all  other  living  struct- 
ures, a  self-formative  power,  and  draws  from  the  blood  the  materials  for 
its  own  nutrition.. 

The  Haversian  canals  vary  in  diameter  from  10100  to  ^5-  of  an  inch, 
the  average  being  about  -g-J-g-.  The  smallest  are  found  near  the  outer  sur- 
face, where  the  bone  is  the  most  compact;  but  they  gradually  become  larger 
toward  the  interior,  where  they  open  out  into  the  cancellous  tissue,  or 
into  the  medullary  cavity.  All,  whatever  their  direction  may  be,  are  sur- 
rounded by  concentric  lamellae  of  bone;  but  the  number  of  the  lamellae 
varies  around  different  canals  from  5  to  15  or  more;  a  smaller  number  in 
young  bone,  and  a  larger  in  old.  All  are  lined  by  a  very  delicate  mem- 
brane, continuous  with  the  periosteum.  The  smallest  canals  contain 
only  a  single  capillary  blood-vessel;  the  larger  contain  a  network  of  ves- 
sels, while  the  largest,  which  gradually  merge  into  the  cancellous  tissue, 
contain  marrow  as  well  as  blood-vessels. 

Here  it  may  be  as  well  to  mention  a  fact  concerning  the  minute  struct- 
ure of  bone,  which  should  never  be  lost  sight  of.  It  is  this: — that  every- 
where underneath  the  membrane  in  contact  with  the  surface  of  bone, 
whether  it  be  the  periosteum  covering  the  exterior,  the  prolongation  of  it 
lining  the  Haversian  canals,  or  the  medullary  membrane  (endosteum) 
lining  the  cancelli,  there  is  a  delicate  layer  of  soft  connective  tissue,  with 
a  multitude  of  small  corpuscles  in  it,  termed  '  osteoblasts.'  Now,  it  has 
been  ascertained  that  these  osteoblasts,  and  the  soft  tissue  in  which  they 


16  HUMAN    OSTEOLOGY. 

are  imbedded,  are  mainly  concerned  in  the  formation  and  the  growth  of 
the  bone;  and  that  by  the  successive  ossification  of  these  tissues,  the  con- 
centric layers  of  bone  are  produced  within  the  Haversian  canals. 

Haversian  Canals  dilated  by  Inflammation. — The  knowledge  of 
the  free  circulation  of  blood  through  the  substance  of  bone  gives  us  the 
key  to  some  of  the  effects  produced  by  inflammation  in  it.  For  example, 
as  inflammation  in  soft  parts  is  attended  by  dilatation  of  the  blood-vessels, 
so  is  it  in  the  case  of  bone.  When  bone  is  actu- 
ally inflamed,  the  blood-vessels  in  the  Haversian 
canals  become  greatly  enlarged,  and  cause  the 
canals  themselves  to  become  larger  by  absorption 
of  the  bone  tissue — so  much  so  as  to  give  the  bone, 
sometimes,  a  reddish  color.  In  operations  where 
the  surgeon  has  to  cut  through  inflamed  bone,  one 
may  see  the  blood  flowing  from  the  cut  surface  of 
the  bone,  as  it  would  from  the  soft  parts.  More  than  this,  the  distended 
blood-vessels  may  occasion  not  only  a  gradual  enlargement  of  the  Haver- 
sian canals,  but  their  inflammatory  deposit  may  cauje  even  a  general 
swelling  of  the  compact  substance  of  the  bone  and  a  natural  separation 
of  its  component  layers,  so  that  it  becomes  light  and  spongy,  as  seen  in 
the  adjoining  figure.13 

Haversian  Canals  obliterated  by  Inflammation.— On  the  other 
hand,  in  some  cases,  e.g.  in  chronic  inflammation,  we  sometimes  find  that 
bones  become  harder  and  thicker  than  natural.  They  may  become  as  hard 
as  ivory,  and  can  take  a  polish.  Here  the  Haversian  canals  are  nearly 
filled  up  by  successive  layers  of  bone.  Indurated  bone  is  therefore  less 
vascular  than  healthy  bone.  A  good  example  of  '  eburnation '  of  bone  is 
occasionally  seen  as  the  result  of  chronic  osteo-arthritis,  where  the  articular 
ends  of  bone  lose  their  cartilage  and  become  hard  and  polished  like  ivory, 
owing  to  the  blocking  up  of  the  Haversian  canals  by  osseous  tissue. 

Lacunae  and  their  Contents. — The  'lacunae'  are  the  insect-like 
cavities  which  we  find  between  the  lamellae,  arranged  in  concentric  circles 
around  the  Haversian  canals.  They  are  characteristic  of  true  bone,  and 
distinguish  it  from  'calcifications',  sometimes  met  with  as  products  of 
disease.  Formerly  the  lacunae  and  canaliculi,  in  consequence  of  their  dark 
color,  were  considered  to  be  solid;  but  later  observations  have  proved 
them  to  be  hollow  spaces.  Each  lacuna  in  the  living  bone  contains  a 
13  From  a  preparation  in  the  museum  at  St.  Bartholomew's  Hospital. 


'>:  'j* 

-  '  830  ,~     ^ 

Si 
«® 


•  w;     ^         •?"  >  .$•/  ^,     m          - 

^'?^f«%'4^| 


Cartilage  cells  enWr^ed  tnd 
V  arranged  m  rows,  separated  by 


._  _  0«teobla«ts  replace  fKe 
eartila^e  e«Ib.  Format™  o 
meduli&ry  spaces. 


Ii  oteculir  r»mmJn»  of 
c«0«f  ied  carb  la^e  «»ted 
with  tfiin  layer  of  bone. 


1  The  layers  of  boi\»  thicks 

/  as  cs.kifi«d  ma 
I  «bsorb*d. 


Section  of  ossifying  cartilage  at  the  E 


L  actinic  and  Canaliculi, 


Bone  coppuscles 

and  their  processes 

wludi  occupyiljela.cil.Ti SB 

andcanaliculi  of  fiq.4* 


Section  of  ossifying carti1a.J>e.sWin^t:he  loops  cf  Hooa  vessels. 


IVabecube  of  bune . 
Bone  corpuscle  — 


Osteoblas-ts  depositing  bone 
on  trabeculse 


Interspaces  filled  with 
osteoblastic  twsue- 


,;: 


-p 


-,.,:* 


Section  of  a  youn£   parietal  bone  . 


MICROSCOPIC    STRUCTURE    OF    BONE.  17 

soft  nucleated  substance  termed  a  bone  corpuscle,  which  sends  its  soft 
processes  or  'outrunners'  along  the  canaliculi.  The  bodies  in  the 
lacunae  and  canaliculi  circulate  nutritious  matter  through  the  bone.  The 
lacunae  and  canaliculi  can  be  filled  with  Canada  balsam.  It  is  curious 
that  in  the  bones  of  Egyptian  mummies  these  minute  cavities  are  filled 
with  the  bituminous  material.  Such  a  bone  corpuscle,  with  its  processes 
highly  magnified,  is  shown  in  Plate  III.  Fig.  5. 

As  a  rule,  the  lacunae  are  oval  and  flattened,  so  that  one  of  their  broad 
sides  is  turned  toward  the  Haversian  canal.  The  first  ring  of  lacunae 
sends  some  of  its  canaliculi  directly  into  the  Haversian  canal,  while  others 
communicate  with  the  canaliculi  of  the  second  ring,  and  so  on  throughout 
the  whole  system.  The  nutrient  fluid  in  the  perivascular  lymphatics  in 
the  Haversian  canal  enters  the  nearest  canaliculi,  and  then  the  inhabitants 
of  the  nearest  row  of  lacunae,  and  is  gradually  passed  on  to  all  the  others 
in  the  Haversian  system.  One  may  say,  then,  that  the  inhabitants  of 
the  lacunae  are  parts  of  the  machinery  of  the  circulation  and  nutrition  in 
the  bone. 

Size  and  Shape. — In  man,  the  lacunae  measure  about  ^-g-  of  an 
inch  in  their  long  diameter,  and  about  -^^  in  their  short.  It  has  been 
shown  that  they  vary  in  size  and  shape  in  the  four  great  classes  of  ani- 
mals, so  that  by  means  of  this  test  it  can  be  ascertained  with  certainty 
whether  a  given  fragment  of  bone  be  part  of  a  mammal,  a  bird,  a  reptile, 
or  a  fish.  As  this  test  is  equally  applicable  in  the  case  of  fossil  bones, 
it  has  an  important  bearing  upon  the  study  of  geology.  Another  inter- 
esting fact  is,  that  the  size  of  the  lacunae  bears  very  little  relation  to  the 
size  of  the  animals  to  which  they  belong.  They  are  nearly  as  large  in  the 
bones  of  the  little  lizard  as  they  are  in  those  of  the  enormous  extinct  lizard, 
the  Iguanodon.  But  their  size  does  bear  an  exact  proportion  to  that  of 
the  blood  corpuscles  in  the  several  classes  of  animals.  Therefore,  as  am- 
phibia have  the  largest  blood  corpuscles,  so  have  they  the  largest  lacunae.14 

Canaliculi :  Size  and  Office.— Respecting  the '  canaliculi '  (Plate  II. 
Fig.  7),  observe  how  exceedingly  minute  they  are;  that  they  run  off 
from  all  parts  of  the  circumference  of  the  lacunae  and  communicate  most 
freely  with  the  canaliculi  of  the  adjoining  lacunae.  Their  diameters  range 
from  H&OQ  of  an  inch  to  g0?i0'6  °f  an  inch;  but  there  are  some  even 
smaller.  Soft  nucleated  corpuscles,  '  bone  corpuscles/  lie  in  the  lacunae, 
and  have  many  delicate  branching  processes,  by  means  of  which  they  in- 

14  Discovered  by  Mr.  Q.ueckett. 
2 


18  HUMAN    OSTEOLOGY. 

tercommunicate  and  pass  lymph  from  one  to  another.  These  branching 
processes  lie  in  the  canaliculi. 

Lamellae. — The  '  circumferential '  lamellae  encircle  the  shaft  of  the 
bone  (Plate  II.  Fig.  5),  and  result  from  the  bone  growing  in  thickness 
by  a  deposit  of  new  layers  on  the  old  shaft  by  the  deep  layers  of  the  peri- 
osteum. 

The  '  Haversian '  lamellae  are  the  concentric  tubes  of  bone  enclosing  the 
Haversian  vessel  (Plate  II.  Fig.  7).  These  result  from  successive  layers 
of  bone  being  deposited  around  the  Haversian  vessel,  the  one  within  the 
other,  encroaching  more  and  more  on  the  space  in  which  the  vessel  lies. 
This  process  renders  the  bone  more  dense  in  structure. 

In  transverse  sections  of  fully  formed  Haversian  systems  there  appear 
to  be  from  five  to  fifteen  concentric  rings  of  bone  varying  in  thickness 
from  y^  to  ^gVjj-  of  an  inch. 

The  ill-defined  and  interrupted  layers  apparent  here  and  there  in  the 
spaces  between  Haversian  systems  are  termed  ' interstitial  lamellae'  (Plate 
II.  Fig.  7).  It  seems  doubtful  how  these  interstitial  lamellae  were  origi- 
nally formed;  16  it  maybe  that  they  are  the  remnants  of  Haversian  systems 
that  have  been  partially  removed  by  absorption. 

Nails  (Claviculi)  of  Gagliardi. — In  carefully-made  preparations  of 
decalcified  bone,  it  may  be  seen  that  its  constibuent  lamellae  are  connected 
by  fibres  which  perforate  them  either  at  a  right  or  an  oblique  angle,  and 
thus  f  bolt '  them  together.  These  '  perforating  fibres '  or  bolts  appear  to 
answer  a  mechanical  purpose.  They  are  best  shown  by  separating  the 
lamellae.  Thus  you  see  not  only  some  of  the  bolts  pulled  out,  but  also 
the  holes  through  which  they  passed.18 

Osseous  Granules. — The  earthy  salts  are  deposited  in  the  animal 
matrix  in  the  form  of  exceedingly  minute  granules.  The  Germans  call 
them  'bone  crumbs.'  We  cannot  see  them,  however,  without  a  magnify- 
ing power  of  1,200  diameters  (Plate  II.  Fig.  6).  They  vary  in  size  in  dif- 
ferent specimens  of  bone.  In  man  their  size  ranges  from  6o\6  to  14^0o  of 
an  inch.  They  can  be  very  distinctly  seen  in  the  skulls  of  small  birds — 
the  canary,  for  instance — and  also  in  the  skull  of  the  bat,  where  they  are 
so  much  larger  than  in  the  human  subject.  After  a  section  of  bone  has 
been  steeped  for  some  time  in  dilute  hydrochloric  acid,  these  earthy  par- 

15  '  Philosoph.  Trans,'  1853.     Messrs.  Tomes  and  De  Morgan. 

16  First  described  by  Domenico  Gagliardi,  Professor  of  Medicine  at  Rome  in  the 
seventeenth  century.  Anatomie  Ossium  novis  inventis  illustrata.  Romae,  1689,  in  8vo. 


.MICROSCOPIC    STRUCTURE    OF    BONE. 


19 


tides  will  be  dissolved  out  of  the  animal  matrix,  and  the  little  cavities  in 
which  they  are  imbedded  can  then  be  distinctly  seen. 

Found  in  Pus  from  Dead  Bone. — It  is  an  interesting  and  valuable 
practical  fact,  that  these  earthy  granules  are  generally  present  in  the 
pus  which  comes  from  dead  bone.  If  a  specimen  of  pus  under  such  cir- 
cumstances be  examined  with  a  power  of  500  diameters,  a  number  of 
earth  granules  may  be  detected  among  the  pus  cells,  proving  that  there  is 
dead  bone  somewhere. l7  In  pus  coming  from  diseased  bone  there  is  as 
much  as  two  and  a  half  per  cent,  of  phosphate  of  lime.18 

Articular  Bone. — By  articular  bone  we  understand  a  thin  layer  of 
bone  situated  immediately  under  articular  cartilage;  and  since  there  is  a 
peculiarity  about  the  structure  of  it,  we  will  allude  to  it  here.  If  a  section 
be  made  perpendicularly  through  the 
articular  surface  of  any  fresh  bone  with 
the  cartilage  attached,  it  will  be  ob- 
served (as  seen  in  Fig.  7)  that  the  car- 
tilage does  not  rest  immediately  upon 
the  cancellous  tissue  of  the  bone,  but 
upon  a  thin  compact  crust  of  bone 
which  closes  the  cancelli.  This  crust, 
which  we  call  '  articular  bone,'  varies 
in  thickness,  and  is  of  a  remarkably 
white  color.  But  its  chief  peculiarity 
consists  in  this — that  it  has  no  Haver- 
sian  canals,  and  therefore  is  not  vascu- 

FIQ.  7.— Structure  of  Articular  Bone. 

fetr.  The  blood-vessels  of  the  cancel- 
lous tissue  run  up  only  as  high  as  its  under  surface,  and  then  turn  back 
in  loops.  Moreover,  its  '  lacunae '  are  three  or  four  times  larger  than  in 
ordinary  bone,  and  are  destitute  of  canaliculi.  This  layer  of  bone  has  no 
Ilaversian  canals,  is  much  less  porous  than  common  bone,  and  in  conse- 
quence of  its  closer  texture  is  all  the  stronger,  and  supports  the  articular 
cartilage  on  a  very  unyielding  surface. 

Although  articular  bone  and  adult  articular  cartilage  have  no  blood- 
vessels in  health,  yet  they  both  become  vascular  in  some  cases  of  disease 
of  the  curtilage.  .  Blood-vessels,  when  well  injected,  may  then  be  seen 
shooting  up  through  the  heretofore  nonvascular  layer  of  bone,  into  the 
cartilage  on  its  surface. 


tt  Upper  cartilage  cells. 


b  Lower  cartilage  cells. 


O  Articular  bone. 


d  Bone  of  the  shaft. 


Mr.  Queckett. 


Mr.  Brausby  Cooper. 


20  HUMAN  OSTEOLOGY. 

STEUCTTJEE  AKD  VAEIETIES  OF  CAETILAGE. 

Varieties  of  Cartilage. — Cartilage,  commonly  called  '  gristle/  is 
tough,  flexible,  and  more  or  less  elastic.  There  are  several  kinds  of  it, 
which  have  functions  varying  with  their  position  and  structure.  It  con- 
sists of  nucleated  cells  embedded  in  a  matrix  or  intercellular  substance. 

Hyaline  Cartilage. — Where  the  matrix  is  translucent  and  structure- 
less it  is  called  hyaline  cartilage.  Nearly  the  entire  skeleton  of  the  foetus 
has  this  structure  at  some  time  or  another  as  well  as  the  white  cartilage 
covering  the  articular  ends  of  bones. 

White  Fibro-Cartilage. — The  intercellular  substance  may  be  white 
and  fibrous,  then  it  is  called  'white  fibro-cartilage/  This  variety  is  but 
slightly  elastic,  and  the  cells  are  small  and  scattered  (Plate  II.  Fig.  1). 
The  intervertebral  substance  consists  mainly  of  this  variety  as  well  as 
the  interarticular  fibro-cartilages. 

Yellow  Fibro-Cartilage. — The  gristle  of  the  ear,  epiglottis,  and 
the  Eustachian  tube  is  of  a  yellow  color,  is  very  elastic,  and  its  intercellu- 
lar substance  consists  of  long  interlacing  wavy  fibres.  It  is  therefore 
named  'yellow  fibro-cartilage.'  The  cells  in  this  variety  are  large  and 
arranged  in  fusiform  rows,  each  row  containing  from  4  to  6  cells. 

Cellular  Cartilage. — As  early  as  the  fourth  week  of  fetal  life,  when 
the  embryo,  is  but  f  of  an  inch  long,  the  principal  part  of  the  skeleton  is 
mapped  out  by  the  formation  of  firm  masses  of  cells  called  '  cellular '  car- 
tilage. (Plate  II.  Fig.  3.) 

Cartilaginous  Skeleton. — A  week  later  an  intercellular  substance 
has  developed  in  this  cellular  cartilage,  converting  it  into  '  hyaline '  carti- 
lage, and  giving  it  greater  solidity.  Thus,  the  whole  foetal  skeleton,  with 
the  exception  of  the  skull-cap  and  the  bones  of  the  face,  consist  at  one 
time  of  hyaline  cartilage. 

At  the  fifth  week  bony  substance  begins  to  be  deposited  in  the  middle 
of  the  clavicle;  at  the  sixth  week  in  the  lower  jaw;  and  by  the  seventh 
week,  when  the  foetus  is  abont  an  inch  long  (Norm.  Hum.  Ost.,  No.l),  a 
small  deposit  of  bone  has  made  its  appearance  in  the  middle  of  nearly  every 
bone  in  the  body.  The  points  at  which  the  bony  deposit  commences  in 
a  bone  are  called  its  '  centres  of  ossification/  It  will  th'erefore  be  under- 
stood that  the  deposition  of  bone  does  not  take  place  at  the  same  time  in 
all  parts  of  the  cartilage,  but  only  about  these  'centres  of  ossification.' 
Meaning  of  Centres  of  Ossification. — Every  bone  has  a  definite 


OSSIFICATION.  21 

number  of  these  centres,  which  always  appear  in  the  same  place;  and 
from  these  centres  the  ossification  extends  according  to  a  regular  plan. 
The  number  of  centres  varies  in  different  bones.  Some  bones  have  only 
a  single  centre;  others  two,  three,  five,  seven,  etc. ;  and  the  bone  called 
the  'sacrum'  has  as  many  as  thirty-three  centres  from  which  its  ossifica- 
tion is  completed. 

Observe,  the  centres  of  any  given  bone  do  not  all  appear  at  once;  some 
appear  before  birth,  others  after  it,  but  all  in  regular  succession,  and  at 
stated  periods,  according  to  the  degree  of  importance  of  the  bone,  and 
the  function  which  it  has  to  perform;  e.g.  the  lower  jaw  and  the  ribs  ossify 
early,  because  suction  and  respiration  are  brought  into  play  at  birth. 
As  a  general  rule,  each  centre  appears  first  in  the  middle  of  the  cartilage; 
and  thence  the  ossification  extends  toward  the  circumference  in  the  flat 
bones,  and  toward  the  extremities  in  the  long  bones.  Almost  all  the 
bones,  then,  in  infancy  and  childhood  are  made  up  of  so  many  distinct 
bony  pieces  united  together  by  cartilage;  and  these  several  pieces  remain 
distinct  until  the  stature  of  the  individual  is  complete,  after  which  they 
are  all  consolidated. 

Perichondrium. — All  kinds  of  cartilage,  with  the  exception  of  that 
which  covers  the  ends  of  the  bone  (articular  cartilage),  are  invested  with 
a  white  fibrous  membrane,  termed  '  perichondrium.'  This,  like  the  peri- 
osteum of  the  bones,  contains  plexuses  of  blood-vessels  ramifying  all  over 
the  cartilage. 

Cartilage  contains  no  blood-vessels.  But  when  diseased,  it  has  been 
proved  by  injection  that  blood-vessels  do  shoot  into  the  cartilage  through 
the  layer  of  articular  bone  beneath  it.19 

Ossification  of  Femur. — As  an  example  of  what  can  be  seen  of  the 
process  of  ossification  with  the  naked  eye,  let  us  follow  out  that  of  the 
thigh-bone  (Plate  IV.  Figs.  1  to  6).  The  future  bone  is  at  first  sketched 
out  in  hyaline  cartilage.  About  the  seventh  week  after  conception,  the 
first  centre  of  ossification  appears  in  the  middle  of  the  shaft — as  is  the 
case  in  all  the  long  bones  (Fig.  1).  From  this  point  ossification  gradually 
extends  up  and  down  the  shaft,  which  is  all  ossified  before  the  other  cen- 
tres appear.  About  the  last  month  of  foetal  life,  a  second  centre  appears 
in  the  lower  endj  which  forms  the  knee  (Fig.  3).  About  the  end  of  the 
first  year  after  birth,  a  third  centre  appears  at  the  upper  end  or  head  of 

19  See  '  Catalogue  of  Histological  Series,1  Mus.  Roy.  Coll.  Surg.,  vol.  i.  plate  viii. 

Fig.  11. 


22  HUMAN   OSTEOLOGY. 

the  bone  (Fig.  4).  In  the  course  of  the  fourth  year,  a  fourth  centre 
appears  in  the  projection  termed  the  *  trochanter  major'  (Fig.  5).  In  the 
course  of  the  fourteenth  or  fifteenth  year  a  fifth  and  last  centre  appears 
in  the  'trochanter  minor'  (Fig.  6). 

'Diaphysis'  and  'Epiphysis.' — Thus,  then,  the  thigh-bone  has 
five  centres  of  ossification.  The  shaft  or  body  of  the  bone,  which  ossifies 
first,  is  called  the  f  diaphysis; '  the  other  parts  are  termed  '  epiphyses.'  As 
these  epiphyses,  during  the  period  of  growth,  are  only  united  to  the  shaft 
by  a  layer  of  cartilage,  the  separation  of  an  epiphysis  by  violence  is  not 
an  unfrequent  accident  in  childhood.  When  growth  is  complete,  all  the 
epiphyses  are  consolidated  with  the  rest  of  the  bone,  and  no  cartilage 
remains  except  at  the  articular  surfaces,  where  there  is  a  thin  layer  of  it 
which  breaks  the  shocks  at  the  joints.  An  '  epiphysis,'  therefore,  is  a 
portion  of  bone  growing  upon  another,  but  separated  from  it  by  cartilage. 

Order  of  Union  of  Epiphyses  to  Shaft.— It  is  worth  observing,  in 
the  long  bones,  that  the  epiphyses  of  that  end  toward  which  the  canal 
for  the  medullary  artery  runs,  are  the  last  to  commence  to  ossify. 

It  is  a  curious  fact,  also,  that  the  order  in  which  the  epiphyses  unite 
to  the  shaft  of  a  bone  is  just  the  reverse  of  that  in  which  they  begin  to 
ossify.  Thus,  the  epiphysis  of  the  trochanter  minor,  though  ossifying 
last,  unites  first.  The  same  may  be  said  of  the  trochanter  major,  of  the 
head  of  the  femur,  and,  lastly,  of  the  lower  end.  At  the  age  of  twenty- 
one,  or  near  it,  they  have  all  united  to  form  a  single  bone.  The  fibula  is 
the  only  exception  to  the  above  rules,  its  lower  epiphysis  ossifying  first 
and  uniting  first  to  the  shaft. 

In  Sauropsida,  the  place  of  the  epiphyses  is  taken  by  thick  pads  of 
cartilage,  which  gradually  ossify  from  the  shafts.  These  are,  therefore, 
not  true  epiphyses.  Birds,  however,  have  a  centre  of  ossification  which 
appears  in  the  upper  projection  of  cartilage  on  the  tibia.  This  may  be 
seen  in  the  leg  of  a  common  fowl. 

Advantages  of  several  Centres. — The  fact  that  bones  are  developed 
from  several  ossific  centres,  separated  by  layers  of  cartilage,  is  advanta- 
geous to  the  growing  animal.  For  example,  it  is  necessary  to  have  the  shaft 
of  a  bone  ossified  to  support  weight,  while  other  parts  remain  cartilage  and 
diminish  concussion,  thus  acting  as  buffers.  '  The  young  lamb  or  foal,'  to 
use  the  words  of  Professor  Owen,  '  can  stand  on  its  four  legs  as  soon 
as  it  is  born;  it  lifts  its  body  well  above  the  ground,  and  quickly  begins 
to  run  and  bound.  The  shock  to  the  limbs  themselves  is  broken  and  cli- 


Ffc.6. 


ft 


showing  the  iprmatioriof 


larietal  bone  of  aTcebus. 


.Haversian  canals 


Cells  from  TOE  tiCl  ma.rrcv/. 


Section 


OSSIFICATION.  23 

minished  at  this  tender  age  by  the  division  of  the  supporting  long  bones 
— by  the  interposition  of  the  cushions  of  cartilage  between  the  diaphyses 
and  the  epiphyses/ 

We  see,  moreover,  a  definite  use  in  separate  centres  of  ossification  for 
the  bones  of  the  head,  not  only  as  facilitating  growth,  but  also  the  process 
of  birth.  The  bones  of  the  skull-cap,  being  connected  only  by  membrane, 
overlap  each  other  a  little  during  parturition,  and  thus  a  large  head  is  ad- 
mitted through  a  comparatively  small  pelvis. 

Bones  developed  in  Membrane. — Most  of  the  bones  in  the  human 
body  pre-exist  in  the  shape  of  cartilage,  and  form  what  is  called  the  '  car- 
tilaginous skeleton,'  which  supports  the  embryo.  But  there  are  some 
bones  which  do  not  pre-exist  as  cartilage,  and  are  formed  directly  in  mem- 
brane, namely,  the  bones  of  the  skull-cap  (the  frontal  bone,  the  parietal, 
the  upper  half  of  the  occipital,  the  squamous  and  tympanic  parts  of  the 
temporal);  also,  the  bones  of  the  face;  and  lastly,  the  inner  plate  of  the 
pterygoid  process  of  the  sphenoid.  In  short,  none  of  the  bones  of  the 
skull  pre-exist  as  cartilage,  except  those  which  form  the  base  of  the  skull. 
The  base  is  sketched  out  in  cartilage  at  a  very  early  period  of  fcetal  life, 
and  forms  a  support  to  the  young  brain.  The  cap  of  the  skull,  at  the  time 
we  are  speaking  of,  is  simply  membranous. 

Ossification  in  Membrane. — We  will  examine  first  what  can  be  seen 
of  the  formation  of  bone  in  membrane  with  the  naked  eye,  taking  the 
parietal  bone  as  an  example.  In  the  early  embryo  (Norm.  Hum.  Ost., 
Nos.  1  to  43)  the  covering  of  the  brain  is  composed  of  two  closely  united 
membranes — an  outer,  termed  the  '  pericranium J;  and  an  inner,  termed 
the  '  dura  mater ' :  between  these  the  bone  is  laid  down.  About  the  end 
of  the  second  month  after  conception,  a  centre  of  ossification  appears  in 
the  middle  of  the  space  which  is  to  be  occupied  by  the  parietal  bone. 
From  this  point  the  deposition  of  bone  spreads  in  radiating  fibres  (Plate 
IV.  Fig.  7).  Similar  centres  of  ossification  appear  simultaneously  in  other 
parts  of  the  soft  covering  of  the  brain,  and,  radiating  in  the  same  man- 
ner, sketch  out  the  rudiments  of  the  several  bones  of  the  skull-cap.  For 
some  time  the  individual  bones  are  connected  simply  by  membrane;  and 
even  at  birth  they  can  overlap  each  other  a  little,  and  so  facilitate  partu- 
rition. Long  after  birth,  indeed,  there  are  parts  of  the  skull-cap  closed 
in  by  membrane  only,  as  every  one  knows  who  has  felt  the  head  of  an  in- 
fant (Plate  XVIII.  Fig.  4).  These  unossified  parts  are  called  the  '  fon- 
tanelles/  from  the  visible  pulsations  of  the  brain  beneath  them,  like  the 


24 


HUMAN    OSTEOLOGY. 


welling  up  of  a  spring.  As  the  child  grows,  the  rays  from  the  edges  of 
the  bones  meet  and  dovetail  so  as  to  form  what  are  called  the  *  sutures ' 
(Plate  XVIII.  Fig.  2).  For  a  long  period  of  life  the  sutures  may  be  sepa- 
rated; indeed,  a  thin  film  of  animal  matter  is  left  unossified  between  the 
interlocking  teeth  of  the  bone,  which  considerably  diminishes  the  shock 
to  the  brain  from  a  blow  on  the  cranium.  As  old  age  creeps  on,  even  this 
film  of  animal  matter  ossifies,  and  the  cap  of  the  skull  becomes  a  solid 
dome  of  bone,  with  all  trace  of  the  sutures  lost. 

Microscopic  Examination. — Let  us  now  study  what  can  be  learned 
with  the  microscope  of  the  process  of  ossification  in  membrane,  taking 
that  of  the  parietal  bone  as  an  example. 

The  membrane  or  animal  basis  to  be  ossified  is  composed  of  fibres  like 
those  of  common  connective  tissue.  The  fibres  interlace  freely  and  the 
meshes  between  them  are  filled  with  blood-vessels  and  closely  packed 
granular  corpuscles  termed  '  osteoblasts.'  These  are  all  the  materials  re- 
quired for  bone  building. 

Changes  in  the  Membrane. — The  centre  of  ossification  is  at  the 
(future)  parietal  eminence.  Just  before  the  appearance  of  the  bone  salts, 
the  membrane  becomes  thicker  and  more  vascular.  Its  component  fibres 
radiate  in  thicker  bundles  from  the  centre  toward  the  circumference, 
sketching  in  advance  the  lines  in  which  the 
bone  is  to  be  laid.  Meantime  the  '  osteoblasts' 
have  enormously  multiplied. 

Osteoblasts:  their  Function.  —  The 
'  osteoblasts '  (bone  buds  or  germs)  are  granu- 
lar nucleated  corpuscles  about  the  size  of  the 
colorless  corpuscles  of  the  blood.  They  are  so 
named  because  they  and  their  descendants  ap- 
pear to  take  most  important  parts  in  the  actual 
formation  of  bone.  It  is  probable  that  they 
are  not  all  destined  to  a  like  future.  But  one 
of  their  chief  functions  appears  to  be  to  ab- 
stract from  the  blood  the  bone  salts,  to  deposit 
them  in  and  around  the  fibres  of  the  mem- 
brane, and  to  become  themselves  ossified,  and 
buried  in  the  fabric  of  the  bone,  as  the  bricks  of  a  building  are  in  the 
mortar.  From  the  centre  of  ossification  the  deposit  of  bone  shoots  out  in 
needle-like  rays  (trabeculffi)  toward  the  circumference,  as  shown  in  the 


FIG.  8. — Diagrammatic  sketch  of 
part  of  an  Ossifying  Parietal  Bone 
of  a  Four  Months' "Foetus.  (From 
a  Preparation  in  the  Museum  of  the 
R.  C.  of  Surgeons.) 


OSSIFICATION.  25 

annexed  wood-cut  (Fig.  8).  Under  a  high  power  the  rays  of  bone  can 
be  seen  covered  with  layers  of  osteoblasts,  which  successively  ossify,  and 
thus  the  trabeculae  grow  in  thickness.  The  best  place  to  study  the  process 
is  at  the  points  of  the  rays  where  the  membrane  is  more  or  less  transpar- 
ent. The  dark  rays  may  be  seen  lying  amongst  the  crowd  of  osteoblasts, 
and  some  of  the  osteoblasts  in  various  stages  of  ossification  upon  the  rays. 
We  may  thus  infer  how  the  bone  grows  in  extent. 

To  see  how  the  bone  grows  in  thickness,  a  section  should  be  made  across 
the  rays  where  they  are  a  little  thicker.  Such  a  section  (Fig.  9)  shows 
that  the  rays  become  connected  by  cross  arches,  and  thus  form  channels  in 


A.  Periosteum. 

B.  Trabecute  of 

bone. 

Osteoblasts  with 
blood-vessels. 

FIG.  9.— Vertical  Section  through  an  Ossifying  Parietal  Bone. 

which  the  blood-vessels  and  bone-building  materials  lie.  These  channels 
are  the  Haversian  canals.  Seme  of  them  remain  as  cancellous  tissue; 
others  are  gradually  filled  by  the  ossification  of  concentric  layers  of  os- 
teoblasts and  become  Haversian  systems.  (Plate  IV.  Fig.  8.) 

Bone  Corpuscles :  Origin. — The  interesting  but  difficult  question 
as  to  the  origin  of  the  bone  corpuscles  and  their  connecting  processes  has 
been  for  many  years  under  .discussion.  But  the  now  generally  accepted 
doctrine  is,  that  they  are  developed  from  some  of  the  osteoblasts.  It  has 
been  already  observed  that  the  osteoblasts  have  probably  not  all  the  same 
future.  It  is  the  destiny  of  some  to  become  ossified.  It  may  be  the  des- 
tiny of  some  to  become  marrow  cells:  while  others  are  destined  to  be  de- 
veloped into  bone  corpuscles,  and  perform  their  allotted  functions  shut 
up  in  their  bony  crypts  (lacunae)  and  their  connecting  processes  in  bony 
tubes  (canaliculi).  The  evidence  of  this  development  of  osteoblasts  into 
bone  corpuscles  is  derived  from  the  fact  that  some  of  them  can  be  seen  in 
the  successive  stages  of  their  transformation. 

Ossification  in  Cartilage. — We  will  now  endeavor  to  explain  that 
the  process  of  ossification  in  cartilage,  rightly  understood,  is  essentially 
like  ossification  in  membrane.  In  both  cases  the  materials  for  bone-build- 
ing are  similar,  namely,  connective  tissue,  blood-vessels,  and  the  little  cor- 
puscles termed  'osteoblasts.'  The  old  school  used  to  teach  that  the  carti- 


26  HUMAN    OSTEOLOGY. 

lage  was  directly  transformed  into  bone  tissue.  But  this  is  not  the  modern 
doctrine.  The  microscope  has  proved  that  the  cartilage  is  only  a 
temporary  structure,  that,  having  answered  a  temporary  purpose,  it  is  re- 
moved, and  that  true  bone  tissue,  of  which  the  materials  are  derived 
from  the  periosteum,  is  substituted  in  its  place  as  a  new  product. 

Previous  to  its  removal  the  cartilage  undergoes  remarkable  structural 
changes,  which  prepare  the  way  and  shape  the  direction  in  which  the 
bone  is  afterward  laid  down.  These  preparatory  changes  are — the  en- 
largement of  the  cartilage  cells,  and  the  calcification  of  the  intervening 
matrix.  If  we  examine  the  calcified  portion  of  the  epiphysial  cartilage 
we  find  there  that  the  cells  are  arranged  in  rows  which  are  parallel  to 
the  axis  of  the  bone.  It  is  this  appearance  which  is  familiarly  known 
as  ossifying  cartilage  (Fig.  11J). 


Periosteum. 


Cartilage  cells  in  calcified  matrix. 

Periosteal  ingrowths  invading  the  car- 
tilage cells. 


Fio.  10.— Diagram  of  Periosteal  Ingrowths  from  the  First  Phalanx  of  Great  Toe  of  a  Fretus. 
(Transverse  Section.) 

As  the  term  calcification  might  be  taken  in  a  wrong  sense,  it  should 
be  clearly  understood  that  it  is  not  the  same  thing  as  ossification.  Cal- 
cification is  the  infiltration  of  an  animal  tissue  with  earthy  salts,  as  in  the 
case  of  shells,  or  in  the  cranium  of  cartilaginous  fishes.  Ossification 
means  the  formation  of  true  bone — a  highly  organized  structure.  Calci- 
fication, in  the  process  before  us,  is  the  forerunner  of  ossification. 

Thus  much  premised,  let  us  examine  the  process  of  ossification  as  ob- 
servable in  the  cartilaginous  shaft  and  at  the  epiphysial  ends  of  what  is 
to  be  a  long  bone. 

Calcification  of  Cartilaginous  Matrix. — The  process  begins  by  the 
appearance  of  an  opaque  spot  in  the  centre  of  the  miniature  shaft.  This 
opacity  is  occasioned  by  the  enlargement  of  the  cartilage  cells,  and  the 
calcification  of  the  matrix.  These  changes  spread  gradually  from  the  cen- 


OSSIFICATION-.  27 

tre  up  and  down  the  shaft,  but  stop  short  of  the  ends,  which  are  continu- 
ally growing  in  advance. 

Ingrowths  of  Periosteum. — At  the  same  time  and  to  the  same  ex- 
tent that  the  preceding  changes  are  taking  place  in  the  cartilage,  the  deep 
layer  of  its  surrounding  perichondrium  (future  periosteum)  sends  off 
vascular  shoots  (periosteal  ingrowths)  of  connective  tissue  charged  with 
osteoblasts  which  penetrate  the  calcified  cartilage  and  soon  make  it  hol- 
low; the  enlarged  cartilage  cells  disappearing  one  after  another,  and 
their  places  being  taken  by  the  '  osteoblastic  tissue '  from  the  periosteum 
(see  Fig.  10). 

Crust  of  Bone  around  Shaft. — Pari passu  with  this  tunnelling  of 
calcified  cartilage  by  the  ingrowths,  the  deep  layer  of  the  periosteum  is 


Epiphysis. 

Rows  of  cartilage  cells  in  calcified  matrix. 
Tubular  spaces  filled  with  osteoblastic  tissue. 


Circumferential  crust  of  porous  bone. 
General  medullary  cavity. 

Periosteum. 

(The  dark  spots  throughout  the  diagram 


te  dark  spots  throughout 


FIG.  11.— Diagram  of  a  Longitudinal  Section  of  Foetal  Long  Bone. 

at  work  laying  down  a  gradually  thickening  crust  of  true  bone  around 
the  shaft  (Fig.  11,  d).  This  process  is  not  preceded  by  cartilage,  but  is 
direct  membranous  ossification,  as  in  the  tabular  bones  of  the  skull. 

Summing-up. — To  form  a  a  correct  idea  of  these  separate  processes, 
the  mind  must  grasp  them  as  going  on  all  together,  not  one  after  the  other. 
Their  general  results  may  be  summed  up  as  follows  (Fig.  11): — 1.  The 
cartilage  at  the  middle  is  hollowed  into  a  cavity  (general  medullary)  and 


28  HUMAN    OSTEOLOGY. 

filled  by  osteoblastic  or  bone-building  tissue  and  blood-vessels  (e).  2.  The 
shaft  is  surrounded  by  a  circumferential  crust  of  porous  bone;  the  first 
rudiment  of  the  true  wall  (d).  3.  The  cartilage  toward  the  ends  is  tun- 
nelled (by  periostea!  ingrowths)  into  irregular  tubular  (medullary)  spaces, 
also  filled  with  osteoblastic  tissue  (c).  These  spaces  freely  communicate 
with  the  general  medullary  cavity,  but  are  blocked  toward  the  growing 
ends  by  a  boundary  line  of  cartilage  (b).  It  is  in  these  spaces  that  blood- 
vessels in  injected  preparations  can  be  seen  running  up  to  the  cartilage 
cells.  4.  The  walls  of  these  tubular  spaces  are  formed  by  the  slender  re- 
mains (trabeculse)  of  the  calcified  matrix.  These  slender  remains  serve 
as  the  foundation  upon  which  the  true  bone  is  laid  and  by  which  its  can- 
cellous  architecture  is  directed. 

For  the  more  minute  observation  of  the  process  of  ossification  in  carti- 
lage, it  is  best  to  take  the  '  line  of  ossification '  at  the  epiphysis  of  a  long 
bone.  The  enlarged  diagram  (Fig.  12)  is  intended  to  illustrate  it. 

Near  the  top  of  the  diagram  the  cartilage  cells  are  seen  enlarged  and 
arranged  in  rows  (J).  The  calcified  matrix,  represented  by  dots,  lies 
not  only  between  the  rows,  but  between  the  cells,  so  that  it  makes  trans- 
verse as  well  as  vertical  septa  between  them.  A  little  lower,  we  see  the 
tubular  spaces,  filled  with  the  bone-building  materials,  namely,  osteoblas- 
tic tissue  and  blood-vessels  (c  and  d).  The  blood-vessels  form  loops  along 
the  line  of  ossification,  where  the  osteoblasts,  having  absorbed  the  transverse 
septa  of  calcified  matrix,  are  invading  the  cartilage  cells  which  disappear. 
"We  see  how  the  tubular  spaces  are  formed  by  the  vertical  remains  (trabe- 
culas)  of  the  calcified  matrix;  how  these  spaces  communicate  here  and 
there  with  each  other  where  osteoblasts  have  absorbed  their  walls;  how 
the  remains  (trabeculae)  of  the  calcified  matrix  form  a  basis  upon  which 
the  osteoblasts  are  deposited  and  transformed  into  bone  (e).  The  ossified 
osteoblasts  are  represented  dark  at  the  bottom  of  the  diagram. 

The  actual  appearances  of  the  process  of  ossification  at  the  epiphysis, 
as  seen  under  the  microscope,  are  represented  in  Plate  III.  Figs.  1  and  2. 

Experiments  with  Madder. — That  bones  grow  in  thickness  by  ad- 
ditions to  their  surface,  and  not  by  interstitial  deposit,  is  proved  from  the 
interesting  experiments  made  with  madder.  It  was  accidentally  discovered 
by  Mr.  Belchier,  that  madder  tinges  the  bones  red.  He  gives  the  follow- 
ing account  of  the  circumstances  under  which  the  discovery  was  made.20 
He  happened  to  be  dining  with  a  calico-printer  on  a  leg  of  fresh  pork,  and 
20  '  Philosoph.  Trans. '  for  1736,  vol.  xxxix. 


OSSIFICATION. 


29 


was  surprised  to  observe  that  the  bones,  instead  of  being  white,  as  usual, 
were  red.  On  making  inquiry,  he  found  that  the  pig  had  been  fed  on  the 
refuse  of  the  dyeing  vats,  \vhich  contained  a  large  quantity  of  the  coloring 
substance  of  madder.  This  fact  naturally  attracted  the  attention  of  physi- 
ologists. The  red  tinge  was  found  to  be  communicated  much  more  quickly 
to  the  bones  of  growing  animals  than  to  those  full  grown.  The  bones  of  a 


a.  Epiphysis.    Hyaline  cartilage. 


b.  Rows  of  cartilage  cells  In  calcified  matrix, 
which  is  represented  by  dots. 


c.  Tubular  spaces  filled  with  osteoblastic 
tissue,  consisting  of  osteoblasts,  blood-vessels, 
and  connective  tissue. 


d.  The  dark  lines  represent  blood-vessels  f 
running  up  the  tubular  spaces. 


e.  The  osteoblasts,  transformed  Into  bone  on  4 
the  trabeculae  of  calcified  matrix,  are  repre- 
sented dark.    No  bone  corpuscles  are  shown. 


Fio.  12.— Epiphysial  End  of  the  Shaft  of  a  Long  Bone.    (Enlarged  from  a,  6,  c,  Fig.  11,  with 
the  addition  of  the  Blood- Vessels.) 

young  pigeon  were  tinged  a  rose  color  in  twenty-four  hours.  In  the 
adult  bird  it  took  fifteen  days  to  do  it.  The  effect  of  madder  upon  bones 
depends  upon  this: — The  coloring  principle  of  the  madder  (Rubia  tine- 
tor  um)  has  a  strong  affinity  for  phosphate  of  lime.  It  appears,  however, 
that  the  vegetable  dye  does  not  combine  with  the  phosphate  of  lime  already 
formed,  but  only  with  that  which  is  actually  forming  and  being  deposited 
in  the  bones.  Therefore,  since  the  dye  tinges  only  the  most  recent  de- 


30  irrMAX   OSTEOLOGY. 


posit  of  bone,  it  is  possible  to  produce  alternate  rings  of  white  and  red 
bone,  by  periodically  administering  and  withholding  the  madder  as  an 
article  of  diet.  These  rings  will  be  observed  not  only  at  the  circumfer- 
ence of  the  bone,  but  also  within  the  Haversian  systems. 

Growth  in  Length  of  Bones.  —  Bones  increase  in  length,  not  so 
much  by  interstitial  deposit,  as  by  addition  to  their  ends;  that  is,  by  pro- 
gressive ossification  of  the  layers  of  cartilage  which  intervene  between  the 
ends  of  the  shaft  and  the  epiphyses.  These  layers  of  cartilage  furnish 
the  animal  basis  of  ossification,  by  constantly  growing,  while  they  ossify 
on  their  upper  and  lower  surfaces.  When  the  cartilage  ceases  to  grow, 
ossification  still  goes  on  till  the  component  parts  of  the  bone  are  all  united 
by  bony  matter;  and  thus  the  stature  of  the  individual  is  determined. 
If  from  inflammation  or  other  cause  the  epiphyses  unite  sooner  than  they 
ought  to  do,  then  one  limb  may  be  shorter  than  the  other.  That  bones 
grow  chiefly  by  addition  to  their  ends  was  proved  by  Hunter.  He  intro- 
duced shots  at  definite  distances  into  the  shaft  of  a  growing  bone  of  a 
common  fowl,  and  examined  them  a  fortnight  or  three  weeks  afterward. 
The  distance  between  the  two  shots  was  found  only  half  as  much  increased 
as  the  distance  between  a  given  shot  and  the  end  of  the  bone.  (Phys. 
Ser.  Nos.  188,  189.) 

Value  of  Periosteum.  —  Such  is  an  outline  of  the  structure  and  for- 
mation of  bone.  It  is  a  subject  interesting  not  only  for  its  own  sake,  but 
because  it  helps  us  toward  the  explanation  of  what  we  are  every  day  seeing 
of  the  progress  of  disease,  and  the  repair  of  injuries  in  bone;  and  what  is 
more,  it  helps  us  toward  a  rational  treatment  of  them.  To  give  a  few 
examples.  Look  at  the  value  of  the  periosteum.  Suppose  a  portion  of 
periosteum  to  be  detached  by  injury  or  disease  from  the  surface  of  a  bone, 
a  part  of  the  subjacent  bone  will  run  great  risk  of  dying.  It  will  not 
necessarily  die,  because  its  blood-vessels  may  still  be  filled  from  within, 
owing  to  the  free  communication  between  the  blood-vessels  of  the  perios- 
teum and  those  of  the  marrow.  In  a  case  of  compound  fracture,  where 
there  are  loose  fragments  of  bone,  we  ought  not  to  remove  any  that  are 
still  connected  to  their  periosteum.  Or,  when  a  portion  of  the  skull-cap 
sliced  off  by  a  sabre  cut  adheres  firmly  to  a  flap  of  the  scalp,  the  flap  with 
the  bone  should  be  re-applied,  and  the  cure  will  frequently  be  effected 
without  death  of  bone.  In  the  Hunterian  Museum  are  several  skulls 
which  have  suffered  from  severe  sabre  cuts.  The  portions  of  bone  thus 
sliced  off  were  once  detached,  and  afterward  re-united  a  little  out  of  their 


PERIOSTEOL  31 

proper  places,  BO  that  the  lines  of  original  separation  and  subsequent  union 
can  be  distinctly  seen.  (Path.  Ser.  Xos.  2892  to  2899).  Again,  there  are 
cases  in  which,  either  from  exposure  to  cold  or  from  direct  injury,  acute 
inflammation  of  the  periosteum  of  the  shaft  of  a  bone  ensues,  effusion  of 
fluid  takes  place  beneath  it,  and  severs  the  connection  between  it  and  the 
bone.  The  death  (necrosis)  of  the  entire  shaft  may  be  the  consequence. 
Then,  what  happens?  As  the  inflammation  subsides,  the  bone-secreting 
layer  of  the  periosteum  forms  new  bone  around  that  which  is  dead,  and 
by  degrees  encloses  it  in  a  bony  case.  The  dead  bone  lies  loose  in  this  new 
case,  having  been  detached  from  the  articular  ends,  which  do  not  die  like 
the  shaft,  and  for  the  reason  that  the  epiphysial  ends  receive  sufficient 
blood  for  their  nutrition  from  the  articular  arteries,  independently  of  what 
they  receive  from  the  shaft.  The  articular  ends  of  the  old  bone  become 
in  time  the  articular  ends  of  the  new.  Thus,  the  periosteum  has  formed 
a  new  shaft  with  a  capacious  cavity  in  its  interior,  in  which  the  old  bone 
is  enclosed,  and  will  remain  so,  and  be  a  source  of  irritation  for  years,  un- 
less removed  by  a  surgical  operation. 

Although  the  periosteum  holds  the  first  rank  of  all  the  structures  which 
repair  bone,  still  we  are  not  to  suppose  that  it  is  absolutely  essential  to  the 
process.  Under  certain  circumstances  we  find  various  other  structures 
becoming  transformed  into  bone.  For  example:  In  a  case  of  compound 
fracture  of  the  leg,  where  a  portion  of  the  entire  circumference  of  the 
tibia,  including  its  periosteum,  was  taken  away,  the  vacancy  in  the  bone 
was  filled  up  by  new  osseous  substance  secreted  by  the  surrounding  soft 
tissues,  and  there  was  no  shortening  of  the  limb.*1  Again,  we  occasionally 
see  the  intervening  soft  tissues  forming  bridges  of  bone,  and  so  repairing 
a  fracture  where  the  broken  ends  themselves  are  widely  apart. 

Material  which  Repairs  Fracture. — Fractures  are  repaired  by  a 
material  similar  to  that  out  of  which  bone  was  originally  formed.  The 
animal  matter  which  is  first  laid  down  is  of  a  fibrous  or  cartilaginous 
nature — or  a  mixture  of  both,  as  the  case  may  be — and  then  earthy  salts 
are  deposited  in  it.  In  the  case  of  a  simple  fracture,  where  the  broken 
ends  are  kept  in  contact  and  perfectly  immovable  by  surgical  appliances, 
the  bones  unite  almost  like  an  incised  wound  of  soft  parts.  After  all  the 
effused  blood  is  absorbed  from  between  the*  broken  ends,  a  soft  fibrous 
substance  (blastema)  full  of  osteoblasts  is  thrown  out  from  the  ends  of  the 
broken  bone,  which  forms  a  thin  layer  of  animal  matter  (intermediate 
11  Stanley,  '  Diseases  of  the  Bones,'  p.  108. 


32  HUMAN    OSTEOLOGY. 

callus)  between  them.  This  gradually  hardens,  and  the  bone  earth  is  then 
deposited  in  the  blastema  and  cells.  So  the  ends  are  united.  This  occu- 
pies a  period  varying  from  four  to  ten  weeks,  according  to  the  bone 
broken;  e.g.  the  clavicle  and  the  ribs  unite  more  quickly  than  other  bones, 
probably  from  their  greater  vascularity.  The  process  is  simply  an  excess  of 
nutrition.  Apparently  more  new  bone  than  is  necessary  is  formed.  The 
excess  fills  up  the  medullary  cavity,  at  the  seat  of  fracture,  and  rounds  off 
corners  if  there  be  any.  But  when  the  permanent  uniting  medium  is 
strong,  all  that  is  seemingly  superfluous  is  gradually  absorbed,  and  the 
medullary  canal  is  restored  to  its  original  condition,  after  a  period  varying 
from  six  to  twelve  months.  On  the  other  hand,  if  the  fracture  be  not 
kept  steady — for  instance,  in  the  case  of  animals — a  kind  of  temporary  splint 
is  formed  in  the  shape  of  a  broad  and  thick  ferule  of  cartilage,  which 
ossifies  around  the  ends  of  the  broken  bone,  and  keeps  them  almost  im- 
movable, while  the  permanent  process  of  repair  is  going  on  between  them. 
This  ferule,  termed  the  provisional  callus,"  does  not  disappear  until  the 
fracture  has  been  thoroughly  repaired. 

22  '  Callus'  is  the  term  applied  by  the  old  surgeons  to  the  materials  by  which  frac- 
tures are  repaired. 


Occipital  .tone, 


~Protu~berance 


eminence 


Tubercle  for  the  attachment  of      ',    "•""'  •' *'^&% 

"the, Superior  constrictor  of  Pharynx       V',^%  ,_     •  /^&**^f$4 


Antrcondylo\d  foramen, 


process 


Groove  fur  sup. 

^x       .-    lonqitwdl      SiriUC. 

mi, 


m 


Occ.ipitaTsitVv 


* 


.  Antrcondyloid   I 
1S          l.fera™,,.^ 

>v"       VZ^iP 

-tminentinnnorri-nata       ^^       _.'      _     '" 

.  Baeilir   ;;: 
groove. 


N'.'Vi 


r  E^ 


»3  roove  ."for 
lateral  sirf: 


—  Irif-'petroszil  sinus. 


BONES  OF  THE  SKULL. 


FOR  convenience  of  description  the  bones  of  the  skull  are  generally 
divided  into  those  which  form  the  '  cranium '  or  brain  case,  and  those 
which  form  the  skeleton  of  the  face.  Each  of  these  will  first  be  described 
separately,  and  afterward  the  skull  will  be  examined  as  a  whole. 


2  Superior  Maxillary,, 

2  Malar, 

2  Nasal, 

2  Palate, 

2  Lachrymal, 

2  Inferior  Turbinated. 

Vomer, 

Inferior  Maxillary. 


(  Occipital, 

J  Frontal, 

14 

2  Parietal, 
BONES  OF        ;: 
f  2  Temporal, 
THE  CRANIUM.    1              ., 
<  Sphenoid, 

BONES  OF   < 
THE  FACE. 

[  Ethmoid, 

THE  OCCIPITAL  BONE. 
(PLATE  V.) 

Foramen  Magnum :  Basilar  Process. — The  occipital  bone  con- 
tributes to  form  part  of  the  base  of  the  skull,  as  well  as  the  back  of  the 
head.  There  is  a  large  oval  hole  in  it,  called  the  '  foramen  magnum/ 
which  transmits  the  spinal  cord  and  its  membranes,  the  two  vertebral 
arteries,  and  the  two  spinal  portions  of  the  spinal  accessory  nerves.  The 
hole  is  very  much  larger  than  the  parts  which  pass  through  it:  all  the 
intervening  space  is  occupied  by  the  cerebro-spinal  fluid  which  supports 
and  protects  the  cord.  The  narrow  part  of  the  bone,  in  front  of  the  hole, 
projects,  with  a  considerable  inclination  upward,  when  the  bone  is  held 
in  its  proper  position — that  is,  with  the  foramen  magnum  horizontal;  it 
is  called  the  '  basilar  process/  because  it  is  wedged  into  the  base  of  the 
skull.  It  is  at  the  top  of  the  pharynx.  This  relation  is  of  practical  im- 


34  HUMAN    OSTEOLOGY. 

portance.  It  is  well  to  know  that  the  basilar  process  is  within  reach  of 
the  finger  when  introduced  deeply  into  the  mouth,  and  that,  conse- 
quently, we  can  explore  it  satisfactorily,  so  as  to  ascertain  how  far  a  poly- 
pus may  be  connected  to  it.  The  end  of  the  basilar  process  is  joined  to 
the  body  of  the  sphenoid  bone,  in  early  life,  by  cartilage;  but  in  the  adult 
this  cartilage  becomes  ossified.  On  its  under  surface  (Plate  V.  Fig.  1) 
we  notice  a  tubercle,  exactly  in  the  middle  line,  to  which  the  aponeurosis 
of  the  pharynx  is  attached;  and  laterally,  rough  surfaces  for  the  attach- 
ment of  the  'rectus  capitis  anticus  major'  and  'minor.'  On  the  upper 
surface  (Plate  V.  Fig.  2)  of  the  basilar  process  there  is  a  gently  sloping 
groove  (basilar  groove),  which  supports  the  '  medulla  oblongata.'  The 
medulla  is  not  in  actual  contact  with  the  bony  groove;  a  thin  layer  of 
fluid  is  interposed,  which,  like  a  water-bed,  protects  this  important  part 
of  the  nervous  system  from  concussion.  On  each  side  of  this  groove  is 
another,  but  much  smaller  (petrosal)  groove,  which  lodges  the  inferior 
petrosal  sinus,  by  which  some  venous  blood  is  returned  from  the 
brain.43 

Occipital  Part. — The  expanded  and  vaulted  part  behind  the  foramen 
magnum  contributes  to  form  the  skull-cap.  On  the  convex  or  cutaneous 
surface,  about  the  middle,  we  notice  a  rough  prominence,  called  the  '  oc- 
cipital protuberance/  plainly  to  be  felt  at  the  back  of  the  head.  From  this 
we  trace  down  to  the  foramen  magnum  what  is  termed  the  '  crest '  of  the 
occiput,  which  gives  attachment  to  the  ligamentum  nuchae  at  the  back  of 
the  neck.  From  this  middle  protuberance  and  crest  trace  outward, 
toward  the  borders  of  the  bone,  two  lines  on  either  side,  termed  the 
'superior  and  inferior  curved  lines.'  These  lines,  as  well  as  the  rough 
surfaces  between  them,  more  or  less  evident  in  different  instances,  indicate 
the  attachments  of  muscles  at  the  back  of  the  neck.  The  precise  attach- 
ments of  these  muscles  are  mapped  out  on  the  right  side  of  the  drawing; 
and  in  examining  them,  understand,  once  and  for  all,  that  the  blue  outline 
denotes  the  insertion  of  a  muscle;  the  red,  the  origin.  It  is  right  to 
explain  that  the  origin  of  a  muscle  is  the  term  applied  to  its  most  gen- 
erally fixed  attachment;  the  insertion  of  a  muscle  is  the  attachment  which 
is  usually  the  more  movable.  However,  it  should  be  understood  that  a 

98  The  term  'sinus'  is  used  very  vaguely  in  anatomy.  It  means,  generally,  the 
hollow  of  anything.  Thus  the  air-cavities  in'the  bones  of  the  head  are  termed  '  sinuses' 
When  used  in  reference  to  the  brain,  a  'sinus'  means  a  channel  formed  by  the  fibrous 
membrane  (dura  mater)  of  the  brain,  for  the  return  of  its  venous  blood. 


OCCIPITAL   BONE.  35 

precise  rule  cannot  be  laid  down  with  regard  to  these  terms  as  applied  to 
muscles,  since  the  origin  or  fixed  attachment,  and  the  insertion  or  mova- 
ble one,  may  under  altered  conditions  be  reversed. 

Thus,  the  bone  near  the  superior  curved  line  gives  origin  to  the  '  tra- 
pezius '  and  '  occipito-frontalis/  and  insertion  to  the  '  sterno-cleido-mas- 
toideus'  and  '  splenius  capitis.'  The  surface  between  the  two  lines  gives 
insertion  to  the  '  complexus.'  Below  the  inferior  line  are  the  insertions  of 
the  '  rectus  capitis  posticus  major,'  the  *  rectus  capitis  posticus  minor/ 
and  the  'obliquus  superior/ 

Condyles  and  Condyloid  Foramina. — The  articular  processes  called 
the  '  condyles '  are  placed  one  on  either  side  of  the  foramen  magnum  along 
its  anterior  half.  They  are  kidney-shaped  and  convex,  with  their  anterior 
ends  converging.  Moreover,  they  slant  so  that  their  inner  margins  are 
lower  than  their  outer;  and  they  thus  fit  into  the  '  cups '  of  the  '  atlas '  or 
first  cervical  vertebra.  Owing  to  this  arrangement,  and  the  great  strength 
of  the  connecting  ligaments,  dislocation  of  the  head  from  the  atlas  is  ex- 
ceedingly rare.  More  than  this,  by  fitting  together  the  two  bones,  you  find 
that  the  condyles  of  the  occiput  are  much  longer  than  the  cups  which 
receive  them;  this  permits  the  backward  and  forward  motion  of  the  head. 
On  the  inner  side  of  each  condyle  is  a  rough  surface  or '  tubercle/  to  which 
are  attached  the  '  odontoid '  or  '  check  ligaments '  which  limit  the  rotation 
of  the  head.  Outside  each  condyle  is  the  'anterior  condyloid  foramen.' 
The  direction  of  this  foramen  is  outward  and  forward.  It  gives  passage 
to  the  '  hypoglossal '  or  ninth  nerve,  which,  proceeding  from  the  medulla 
oblongata,  is  distributed  to  the  muscles  of  the  tongue.  Immediately 
above  the  '  anterior  condyloid  foramen/  or  canal,  as  it  should  be  called, 
there  is  a  heaping-up  of  bone,  which,  not  having  received  a  name,  may 
be  termed  the  '  eminentia  innominata.'  It  looks  like  a  strong  bony  bridge 
over  the  canal,  and  strengthens  the  base  of  the  skull  like  a  flying  arch 
just  over  the  condyle.  Behind  each  condyle  is  a  deep  depression  or 
'  fossa/  at  the  bottom  of  which  is  mostly  found  a  '  posterior  condyloid 
foramen.'24  The  fossa,  by  making  room  for  the  cups  of  the  atlas,  enables 
us  to  move  our  heads  further  backward  than  we  otherwise  could  have 
done;  and  the  foramen  at  the  bottom  of  it  is  the  opening  of  a  canal 
which  runs  horizontally  forward  into  the  '  groove  for  the  lateral  sinus ' 

24  In  some  skulls  there  are  no  'posterior  condyloid  foramina.'  In  fifty  skulls 
which  I  have  examined  I  find  them  more  frequently  present  than  absent.  Either  the 
right  or  the  left  foramen  may  be  absent. 


36  HITMAN    OSTEOLOGY. 

(Plate  V.  Fig.  2),  and  transmits  a  vein  from  the  lateral  sinus  to  the  ver- 
tebral vein  outside  the  skull. 

Immediately  external  to  the  condyles,  the  bone  forms  on  each  side  a 
projection,  termed  the  'jugular  eminence/  On  its  under  surface  (Plate 
V.  Fig.  1)  there  is  a  roughness  for  the  insertion  of  the  *  rectus  capitis 
lateralis/  On  its  upper  or  cerebral  surface  is  a  deep  'grobve  for  the 
lateral  sinus/  one  of  the  large  venous  canals  which  return  the  blood  from 
the  brain.  Trace  this  groove  forward,  and  observe  that  it  turns  suddenly 
downward,  forming  a  kind  of  gulf,  sometimes  termed  the  '  jugular  fossa ' 
which  lodges  the  commencement  of  the  internal  jugular  vein.  Looking 
at  the  base  of  the  skull  (Plate  XIX.)  observe  further,  that  it  contributes, 
with  the  petrous  part  of  the  temporal  bone,  to  form  the  '  foramen  lacerum 
posterius/ 

Cerebral  Surface. — On  the  concave  surface  (Plate  V.  Fig.  2)  observe 
two  deeply  grooved  thick  ridges  of  bone,  crossing  each  other, — the  one 
vertical,  the  other  horizontal:  these  grooves  contain  the  sinuses  of  the 
brain.  The  groove  of  the  vertical  ridge  contains  the  '  superior  longitu- 
dinal sinus '  above,  and  the  '  occipital  sinus '  below  the  crossing.  Near  the 
foramen  magnum,  the  groove  for  the  occipital  sinus  generally  subdivides 
into  two  smaller  ones,  which  gradually  lose  themselves  around  its  margin. 
The  horizontal  groove  contains  the  great  '  lateral  sinus/  By  referring  to 
Plate  XIX.  this  great  groove  may  be  traced  in  its  winding  course  along 
the  occipital  bone  across  the  posterior  inferior  angle  of  the  parietal  bone, 
the  temporal,  and  then  on  to  the  occipital  again,  down  as  far  as  the  '  fora- 
men lacerum  posterius/  The  grooves  for  the  lateral  sinuses  are  seldom 
of  equal  size  on  both  sides  of  the  skull.  Generally,  the  right  is  larger 
than  the  left;  hence  the  larger  size  of  the  right  internal  jugular  vein. 
Besides  being  grooved  for  the  sinuses,  the  ridges  give  attachment  to  pro- 
cesses of  the  '  dura  mater/  which  support  the  lobes  of  the  brain.  The 
horizontal  ridge  gives  attachment  to  the  '  tentorium  cerebelli/  the  longi- 
tudinal ridge  to  the  '  f  alx  cerebri '  above,  and  the  '  f alx  cerebelli '  below 
the  crossing. 

"Where  the  ridges  cross  each  other,  there  is  a  heaping-up  of  bone, 
termed  the  '  internal  occipital  protuberance/  This  is  by  far  the  strongest 
part  of  the  bone,  and  protects  the  back  of  the  cranium;  besides  which, 
at  this  protuberance,  no  fewer  than  six  sinuses  of  the  brain  meet,  viz.  the 
superior  longitudinal,  the  two  lateral,  the  two  occipital,  and  the  straight. 
The  meeting  of  these  sinuses  is  termed  the  'torcular  Herophili/  Hero- 


OCCIPITAL   BONE.  37 

philus  fancied  that  the  blood  flowing  in  here  would  be  'twisted*  or 


Between  the  ridges  there  are  four  '  fossae '  which  receive  the  lobes  of 
the  brain — the  two  upper,  the  posterior  lobes  of  the  cerebrum,  the  two  lower, 
the  lateral  lobes  of  the  cerebellum.  Hold  the  bone  to  the  light,  and  see 
how  thin  are  the  walls  of  the  fossaa  for  the  cerebellum;  this  is  well  pro- 
tected by  the  mass  of  muscles  at  the  back  of  the  neck. 

Connections. — The  occipital  bone  is  connected  with  six  other  bones; 
namely,  with  the  two  parietals  by  the  remarkably  serrated  '  lambdoid ' 
suture,  with  the  two  temporals,  with  the  sphenoid,  and  with  the  atlas; 
the  latter  being  articulated  to  the  condyles  by  movable  joints.  The 
sutures  are  simply  named  after  the  bones  which  they  connect:  for  in- 
stance, we  speak  of  the  '  occipito-parietal '  suture,  the  '  petro-occipital,' 
the  '  occipito-mastoid,'  and  the  '  spheno-occipital/  All  these  connections 
are  well  serrated,  except  the  '  spheno-occipital/  which  is  quite  effaced  in 
the  adult  skull,  and  the  'petro-occipital.' 

Ossification. — The  occipital  bone  is  developed  from  four  distinct 
centres,  ^  which  appear  about  the  seventh  week  of  foetal  life — one  for  the 
basilar  part,  one  for  the  occipital,  and  one  for  each  condyloid  part  (Nor. 
Hum.  Ost.  No.  35).  These  segments  are,  respectively,  the  'basi-occi- 
pital/  the  '  supra-occipital,'  and  the  two  '  ex-occipital '  foatal  elements  of 
the  bone.  They  all  meet  and  form  the  foramen  magnum,  and  all  are 
distinct  at  birth.  The  occipital  and  condyloid  parts  unite  about  the 
fourth  year;  the  basilar  and  condyloid  about  the  fifth. 

In  very  few  skulls,  there  projects  from  the  lower  surface  of  the  jugular 
eminence  a  more  or  less  prominent  tubercle,  the  l  par-occipital  process.' 
It  is  the  analogue  of  a  transverse  process.  It  is  quite  a  deviation  from 
the  human  type,  but  is  very  constantly  developed  in  the  mammalian 
series.  There  is  a  good  specimen  of  the  process  in  the  Nor.  Hum.  Ost. 
Ser.  (No  747),  in  a  skull  from  an  aboriginal  of  one  of  the  Philippine 
Islands.  The  process  is  even  longer  than  the  mastoid  process,  and  pre- 
sents an  articular  surface  for  joining  the  transverse  process  of  the  atlas. 
There  is  a  similar  process  in  a  skull  in  the  museum  of  St.  Bartholomew's 
Hospital.  There  are  also  two  specimens  of  it  in  the  Museum  of  Anatomy, 
in  Kichmond  Street,  Dublin. 

Comparative  Osteology. — In  all  mammalia,  as  in  man,  there  are 
two  occipital  condyles,  fitting  into  two  corresponding  articular  surfaces 
on  the  atlas.  In  birds  and  reptiles  (Sauropsida),  however,  there  is  but 


38  HUMAN    OSTEOLOGY. 

a  single  occipital  condyle,  in  front  of  the  foramen  magnum,  in  the 
middle  line.  This  should  be  seen  and  noted,  as  it  is  one  of  the  distinc- 
tive features  of  the  above-named  classes.  (See  separate  series  in  the  Mus. 
Roy.  Col.  Surg.) 

The  cells  which  contain  air  and  separate  the  inner  and  outer  tables 
of  the  skull  in  the  frontal  bone  of  man  extend  as  far  back  as  the  occipital 
bone  in  elephants.  See  sections  of  the  elephant's  skull  (No.  2657). 

In  quadrupeds  the  prominence  of  the  crest  and  external  occipital 
protuberance  bears  a  direct  relation  to  the  development  of  the  ligamentum 
nuchae  which  supports  the  head,  and  is  usually  in  proportion  to  the  weight 
of  the  head  and  its  appendages.  Compare  the  head  of  a  deer,  elephant, 
and  tiger  with  that  of  a  man  in  these  particulars.  In  the  moles  the  liga- 
mentum nuchas  will  be  seen  to  be  nearly  all  ossified. 


PARIETAL  BONE. 

(PLATE  VI.) 

This  broad,  roof -like  bone  derives  its  name  from  paries,  a  wall,  as  it 
forms  so  much  of  the  wall  of  the  skull-cap.  It  is  the  only  bone  belonging 
exclusively  to  the  vault  pf  the  cranium.  With  its  fellow  of  the  opposite 
side  it  makes  the  keystone  of  the  arch  which  spaas  the  brain.  The  two 
pillars  of  the  arch  are  the  squamous  portions  of  the  temporal  bones  (Fig. 
23,  skull  as  a  whole).  It  is  convex  on  the  outer  surface,  concave  on  the 
inner,  and  four-sided. 

Outer  Surface. — On  the  outer  or  convex  surface  (Fig.  1),  notice  the 
'parietal  eminence.'  This  is  the  spot  in  which  the  ossification  of  the 
bone  began.  Below  the  eminence  is  a  curved  line,  termed  the  '  temporal 
ridge/  which  gives  attachment  to  part  of  the  '  temporal  aponeurosis.' 
The  surface  below  this  line  forms  part  of  the  '  temporal  fossa/  which  gives 
origin  to  the  '  temporal  muscle.'  The  four  angles  of  the  bone  are  '  anterior 
superior/  'anterior  inferior/  '  posterior  superior/  and  '  posterior  inferior.' 

Cerebral  Surface. — The  concave  cerebral  surface  has  four  kinds  of 
marks  or  impressions  upon  it.  Firstly,  over  the  general  surface  there  are 
large  shallow  grooves  corresponding  to  the  convolutions  of  the  brain. 
Secondly,  along  the  upper  border  is  a  half  groove  for  the  superior  longi- 
tudinal sinus,  and  across  the  posterior  inferior  angle  is  a  complete  groove 


Parietal  Foramen. 


,v-- 

&$ ' 


^al  eminence 


PostrSuprC\. 
Ari^le.  •% 

L  •Wor-mi  an  loonc  -''f^V^ 
*% 

Rg.i.  %g 

.  pV  °"*'                            ****^| 

llfLpor^l^l 

.  ^e^P^— 
.S           c,riJ    tnus' 

Parietal  Bone 


Groove forLonbitudinal  sinus 


An^le 


Groove  for  Lateral  sir 
Groove  for  middle  Menin^eal  Artery 


PARIETAL     BONE.  39 

for  the  lateral  sinus  on  its  way  from  the  occipital  to  the  temporal  bone. 
This  should  be  borne  in  mind  in  articulating  these  bones  with  the  parietal. 
Thirdly,  running  close  to  and  parallel  with  the  anterior  border  is  the 
groove  for  the  middle  meningeal  artery,  from  which  ramify  over  the  rest 
of  the  bone  a  number  of  smaller  channels.  Fourthly,  near  and  along  the 
upper  border  are  seen  a  number  of  rounded  depressions,  which  in  the  re- 
cent state  contained  the  so-called  Pacchionian  bodies.  Toward  the  back 
part  of  the  upper  border  is  mostly  seen  a  foramen  ('parietal  foramen') 
which  transmits  a  vein  from  the  superior  longitudinal  sinus  to  the  outside 
of  the  skull,  and  often  an  artery  from  the  middle  meningeal  to  the  tem- 
poral artery. 

Connections. — The  parietal  bone  is  connected  by  sutures  with  five 
bones  (Plate  XVIII.),  as  follows: — With  the  opposite  parietal  bone,  by 
the  interparietal  or  '  sagittal '  suture;  with  the  frontal  bone,  by  the  fronto- 
parietal  or  '  coronal '  suture;  with  the  temporal  bone,  by  the  temporo- 
parietal  or  'squamous'  suture;  with  the  occipital  bone  by  the  occipito- 
parietal  or  *  lambdoid '  suture,  and  with  the  sphenoid  bone,  by  the  spheno- 
parietal  suture.  In  all  adult  skulls  the  sagittal  suture,  though  for  the 
most  part  extremely  serrated,  is  much  less  so  near  the  parietal  foramina. 
When  obliteration  of  this  suture  takes  place  in  age,  it  always  begins  oppo- 
site these  holes.  Do  not  fail  to  notice  the  beautiful  arrangement  of  the 
sutures  of  the  parietal  bone:  the  sutural  edges  are  bevelled  on  alternate 
sides,  so  that  the  bone  cannot  be  driven  in  without  previous  fracture. 

Ossification. — It  is  developed  from  one  centre,  which  makes  its 
appearance  at  the  parietal  eminence,  about  the  seventh  week  of  foetal  life. 

Fontanelles. — The  term  '  fontanelles '  is  given  to  those  membranous 
intervals  in  the  foetal  skull  which  are  seen  at  the  four  angles  of  the  parietal 
bone.  These  unossified  parts  are  so  called  from  the  pulsations  of  the 
brain  beneath  them,  perceptible  in  infants,  like  the  welling  up  of  water 
in  a  spring.  They  are  produced  in  the  following  manner.  Ossification 
commences  in  the  centre  of  the  bone,  and  advances  toward  the  circumfer- 
ence; therefore,  the  most  distant  parts  of  the  bone  are  the  last  to  be  ossi- 
fied. These  points  are  the  angles  where  the  several  bones  eventually  meet. 
There  are  in  all  six  '  fontanelles '  (Plate  XVIII.  Figs.  4  and  5).  Observe  the 
shape  of  the  anterior  and  posterior  '  fontanelles/  and  of  the  two  lateral. 
The  anterior,  situated  between  the  adjacent  angles  of  the  parietal  bones 
and  the  ununited  halves  of  the  frontal,  is  lozenge-shaped,  and  remains 
open  for  some  time  after  birth;  indeed,  it  is  not  (as  a  rule)  entirely  oblit- 


40  HUMAN    OSTEOLOGY. 

erated  till  the  fourth  year.  The  posterior,  situated  between  the  parietals 
and  the  apex  of  the  occipital  bone,  is  triangular  and  nearly  closed  at  birth. 
These  'fontanelles'  are  of  especial  importance  to  the  accoucheur,  as  by 
the  feel  of  them  the  finger  can  detect,  during  parturition,  the  position  of 
the  head  of  the  child.  The  lateral  '  f ontanelles '  are  of  less  importance, 
and  generally  obliterated  before  birth. 

Right  or  Left? — In  studying  osteology  the  student  must  learn  to  hold 
each  bone  in  a  similar  position  to  the  corresponding  one  in  his  own  body. 
Now  in  order  to  do  this  in  the  case  of  single  bones,  such  as  the  occipital 
or  frontal,  all  that  it  is  necessary  to  know  is  (1)  either  the  top  or  the  bot- 
tom, and  (2)  either  the  front  or  the  back  of  the  bone.  But  in  all  bones 
which  occur  in  pairs  (i.e.  of  which  there  is  a  right  and  left)  six  aspects 
must  be  considered,  viz.  a  top  and  bottom,a  front  and  back,  an  inner  and 
outer  side,  and  it  becomes  necessary  in  them  to  know  three  points  instead 
of  two,  in  order  to  place  them  in  the  required  position,  viz.  (1)  the  top  or 
the  bottom;  (2)  the  front  or  the  back;  and  (3)  the  inner  or  the  outer  side. 
It  is  best  to  choose  the  most  striking  or  obvious  characters  of  a  bone  by 
which  to  determine  these  points,  as  being  the  quickest  way  of  arriving  at 
the  conclusion.  Thus,  taking  the  parietal  bone:  (I)  the  inner  side  is 
recognized  by  its  concave  surface,  which  fits  on  to  the  brain,  and  is  marked 
by  its  convolutions;  (2)  the  bottom  is  known  by  its  arched  edge  for  articu- 
lation with  the  squamous  portion  of  the  temporal  bone;  (3)  the  front 
is  known  by  the  groove  for  the  middle  meningeal  artery  which  runs  up 
close  to  its  edge.  Bearing  in  mind  these  points,  it  is  impossible  to  mis- 
take a  right  for  a  left;  and  with  anything  less  than  these  three  points,  it 
is  equally  impossible  to  know  one  from  the  other. 

Comparative  Osteology. — In  Carnivora  the  temporal  muscles  are  so 
extensive  that  they  meet  in  the  middle  line  of  the  skull,  where  they  are 
attached  to  a  dense  median  crest  of  bone,  which  represents  the  temporal 
ridges  coalesced.  This  is  conspicuous  in  the  skeleton  of  the  tiger.  It  is 
interesting  to  note  that  the  dog  is  not  born  with  this  median  ridge;  at 
birth  the  temporal  muscle  extends  only  partly  up  the  side  of  the  head. 
As  the  dog  grows  the  muscle  rises  further  up  the  head  until  it  meets  its 
fellow  in  the  middle,  and  then  the  ridge  begins  to  be  developed.  This 
progressive  increa&3  of  the  muscle  may  be  due  to  the  habit  puppies 
have  of  worrying  everything  they  meet  with,  or  it  may  be  the  result  of 
an  hereditary  tendency. 


Temporal 
fossa         \ 


Part  of  the  roofoFtVieTsIose 


process 


Nasal  spine 


frontal  $inus__ 
Part  oi-  the  roof  Of  the  Nog 


"         ^Lachrymal  fossa. 
Flace  for  the  -pulley. 
\Grooves  formm^ \N(ththeEtVnnoic!l;< 
tVie  interna.1  orbital  foramina.. 


FRONTAL    BONE.  41 

In  elephants  and  owls  the  inner  and  outer  tables  of  the  parietal  bones 
are  separated  by  enormous  air  cells. 

In  man  the  two  originally  distinct  halves  of  the  frontal  unite  and  form 
one  bone.  In  bats  the  two  parietals,  which  in  us  remain  distinct,  unite 
and  form  a  single  bone;  this  is  also  the  case  in  many  rodents,  as  the  hare, 
but  in  the  rabbit  they  remain  separate.  In  Ruminants  and  Solidungula 
the  parietals  are  united. 


FRONTAL  BONE. 
(PLATE  VII.) 

The  situation  of  the  frontal  bone  is  implied  by  its  name.  As  it  forms 
not  only  the  forehead,  but  the  roof  of  the  orbits,  we  naturally  divide  it 
into  a  ' frontal  plate'  and  an  ' orbital/ 

Frontal  Plate. — The  anterior  surface  of  the  'frontal  plate*  is 
smooth  and  convex,  and  gives  breadth  and  height  to  the  forehead.  Ob- 
serve, first,  the  two  'frontal  eminences,'  one  on  each  side,  familiarly 
called  the  '  bumps '  of  the  forehead.  They  are  the  two  points  from  which 
the  bone  was  originally  formed,  and  their  greater  or  less  prominence  indi- 
cates to  a  certain  extent  the  amount  of  brain  behind  them.  Not  so  the 
two  projections  lower  down,  termed  the  'superciliary  ridges':  these  do 
not  correspond  to  prominences  of  the  brain,  but  are  occasioned  by  air- 
cavities  termed  the  'frontal  cells'  or  ' sinuses,'  situated  between  the  two 
'  tables '  of  the  skull.  And  here  it  may  be  well  to  mention,  that  the  cap 
of  the  skull  consists  of  two  layers  of  compact  bone,  called,  respectively, 
the  outer  and  inner  '  tables '  of  the  skull,  and  separated  by  an  interme- 
diate cancellous  tissue  termed  the  '  diploe.'  We  shall  allude  to  the  advan- 
tage of  this  structure  hereafter  (skull  as  a  whole,  Fig.  20);  meantime, 
observe  that  the  frontal  cells  are  formed  by  the  separation  of  these  tables. 
To  see  the  extent  of  the  cells,  one  ought  to  make  vertical  sections  as 
shown  in  Plate  XXIII. 

The  Frontal  Sinuses. — There  are  some  points  of  interest  about  the 
frontal  sinuses.  1.  They  communicate  freely  with  each  nostril  through  a 
canal  termed  the  '  infundibulum '  (Fig.  2);  therefore  it  is  possible  for 


42  HUMAN    OSTEOLOGY. 

insects  to  reach  them."  A  lady  had  a  kind  of  centipede  (Scolopendra 
electrica)  for  a  year  in  one  of  her  frontal  cells.  It  gave  her  intense  pain, 
and  was  expelled  at  last,  alive,  during  a  fit  of  sneezing.28  It  is  by  no 
means  uncommon  to  find  the  larvae  of  insects  in  the  frontal  cells  of  ani- 
mals. Sir  C.  Bell  states  that  a  man,  having  slept  in  barns,  was  afflicted 
with  pains  in  the  forehead,  '  which  were  relieved  after  he  had  discharged 
from  his  nose  a  worm  belonging  to  that  class  which  spoils  the  corn/  2. 
As  they  are  lined  by  a  continuation  of  the  same  mucous  membrane  which 
lines  all  the  other  passages  of  the  nose,  we  have  a  ready  explanation  of  the 
aching  pain  in  the  forehead  in  cases  of  influenza,  or  a  common  head  cold. 
3.  In  cases  of  fracture  of  the  base  of  the  skull  involving  the  walls  of  the 
cells,  it  is  possible  for  fragments  of  the  brain  to  escape  from  the  nose. 
The  author  has  seen  a  case  of  this  kind  where  the  patient  recovered  with- 
out any  permanent  ill  effects  except  partial  loss  of  smell.  4.  If  the  outer 
wall  of  the  cells  be  injured  by  violence  or  disease,  the  air,  in  sneezing  or 
coughing,  is  liable  to  escape  under  the  skin  of  the  forehead;  this  condi- 
tion is  called  'surgical  emphysema/87  A  boy  was  kicked  by  a  horse  on 
the  forehead,  so  that  the  frontal  cells  were  exposed.  There  resulted  a 
fistulous  opening,  through  which,  when  the  nose  was  held,  he  could  blow 
out  a  candle.  5.  They  not  only  contribute  to  the  lightness  of  the  skull, 
but  increase  the  resonance  of  the  voice.  They  are  not  developed  until 
about  the  age  of  puberty,  and  steadily  increase  in  size  afterward.  In 
some  tribes — for  instance,  in  the  native  Australians — they  are  but  slightly 
developed;28  and  hence  arises  that  want  of  resonance  for  which  their 
voice  is  remarkable.29  Even  in  Europeans  their  size  and  extent  vary 
exceedingly.  A  good  idea  may  be  formed  of  their  size  in  some  persons, 
by  the  fact  that  they  may  lodge  a  musket-ball:  A  soldier  was  wounded 
at  the  battle  of  Talavera  by  a  ball  which  struck  him  on  the  forehead  and 
lodged  in  the  frontal  sinus.  It  was  readily  removed  by  enlarging  the 
opening,  and  the  man  recovered.30  The  author  has  seen  a  case  precisely 
similar,  in  a  soldier  who  was  wounded  in  the  Crimea.  The  sinuses  are 
commonly  separated  by  a  bony  partition,  often  incomplete. 

25  '  Histoire  de  1'Academie  des  Sciences,'  1708,  1733. 

26  Blumenbach. 

27  Hyrtl,  '  Topog.  Anatomie. ' 

28  Professor  Owen. 

29  On  this  subject  see  an  excellent  work  by  Amman,  '  De  Loquela, '  written  in 
1700. 

30  Guthrie,  'Commentaries  on  Surgery,'  6th  edition,  p.  374 


FRONTAL  BONE.  43 

The  '  bumps '  are  not  prominent  in  children,  because  the  tables  of  the 
skull  do  not  begin  to  separate  to  any  extent  before  puberty.  From  an 
examination  of  more  than  100  skulls,  it  appears  that  the  absence  of  the 
external  prominence,  even  in  middle  age,  does  not  necessarily  imply  the 
absence  of  the  sinus  itself,  since  it  may  be  formed  by  a  retrocession  of  the 
inner  table  of  the  skull.  In  old  persons,  as  a  rule,  when  the  sinuses 
enlarge,  it  is  by  the  inner  table  encroaching  on  the  brain  case.  The  skull 
wall  follows  the  shrinking  brain.  The  range  of  the  sinuses  may  extend 
even  more  than  half-way  up  the  forehead,  and  backward  for  an  inch  or 
more  along  the  orbital  plate  of  the  bone.  Sometimes  one  sinus  is  larger 
than  the  other,  and  consequently  the  '  bump '  on  one  side  of  the  forehead 
may  naturally  be  more  prominent  than  that  on  the  other.  In  the  Nor. 
Hum.  Ost.  Ser.  (Nos.  153  to  155)  in  the  Museum  of  the  Eoyal  College  of 
Surgeons,  there  is  an  instructive  collection  of  horizontal  sections  through 
the  frontal  bone  at  the  level  of  the  sinuses.  In  a  specimen  from  a  man 
set.  32,  it  may  be  observed  that  though  the  sinuses  are  very  extensive, 
there  is  no  external  protuberance.  In  another  from  a  man  aet.  47  there 
are  no  sinuses,  yet  there  is  a  great  external  protuberance.  One  obvious 
conclusion  from  all  this  is,  that  the  '  bumps '  on  the  forehead  mapped  out 
in  this  situation  by  phrenologists,  under  the  heads  of  '  Locality/  '  Form/ 
'Time/  '  Size/  etc.,  do  not  necessarily  coincide  with  any  convolutions  of 
the  brain. 

Orbital  Margin. — The  margin  of  the  orbit,  termed  the  *  supra-or- 
bital arch/  is  composed  of  thick  and  massive  bone, — as  is,  indeed,  the 
entire  circumference  of  the  orbit.  But  the  '  internal  and  external  angular 
processes ' — in  other  words,  the  piers  of  the  arch — are  remarkably  strong, 
and  form  buttresses  for  its  support.  Near  the  inner  third  of  the  arch  is 
the  '  supra-orbital  foramen/  or  it  may  be  a  '  notch/  for  the  transmission 
of  the  supra-orbital  nerve  and  artery.  It  is  this  nerve  which  is  affected 
in  '  brow  ague/  At  the  external  angular  process  is  the  starting-point  of 
the  'temporal  ridge/  to  which  the  temporal  aponeurosis  is  attached 
(Plate  XV.  Fig.  2);  and  just  below  this  is  a  little  surface  of  bone  which 
contributes  to  form  the  'temporal  fossa '  for  the  origin  of  the  temporal 
muscle. 

Cerebral  Surface. — On  its  cerebral  surface  (Plate  VII.  Fig.  2),  the 
'  frontal  plate  *  is  concave,  and  mapped  out  by  the  convolutions  of  the 
brain  and  the  grooves  of  the  anterior  meningeal  arteries  (small  vessels 
given  off  from  the  ethmoidal  branches  of  the  ophthalmic),  and  the  rami- 


44  HUMAN   OSTEOLOGY. 

fications  from  the  middle  meningeal  artery,  on  either  side.  In  the  middle 
line  is  the  groove  for  the  commencement  of  the  superior  longitudinal 
sinus.  Trace  the  groove  downward  and  observe  that  its  margins  gradu- 
ally approximate,  and  lead  to  a  small  hole,  the  'foramen  caecum/  The 
foramen  caecum  sometimes  leads  into  the  frontal  sinus,  sometimes  directly 
into  the  nose;  or  it  may  open  on  the  posterior  or  anterior  surface  of  the 
nasal  bones.  It  sometimes  contains  a  small  artery.  Though  called  '  blind/ 
it  generally  transmits  a  small  vein  from  the  longitudinal  sinus  into  the 
frontal  cells;  and  this  is  one  of  the  anatomical  reasons  assigned  why 
bleeding  from  the  nose  relieves  congestion  of  the  brain,  and  why  the  old 
practitioners  were  in  the  habit  of  leeching  the  nose. 

Very  often  the  margins  of  the  groove  for  the  longitudinal  sinus  coa- 
lesce, so  as  to  form  a  small  ridge,  before  they  reach  the  foramen  caecum. 
They  give  attachment  to  a  perpendicular  sheet  of  the  dura  mater  (termed, 
from  its  shape,  the  '  falx  cerebri '),  which  separates  the  hemispheres  of  the 
brain.  Therefore,  when  we  see  a  frontal  bone  with  a  well-marked  ridge 
along  the  beginning  of  the  longitudinal  groove,  it  is  but  the  ossification  of 
part  of  this  fibrous  membrane.  Pieces  of  bone  occasionally  occur  in  the 
falx  cerebri,  which  remind  us  of  the  tentorium  cerebelli  in  some  Carniv- 
ora,  as  tigers,  seals,  and  cats,  in  which  the  tentorium  is  for  the  most  part 
bony  instead  of  membranous  (Nos.  4608  and  4483). 

Orbital  Plates.— The  'orbital  plates'  (Plate  VII.  Fig.  2)  extend 
horizontally  backward,  and  form  a  concave  roof  for  the  orbit,  and  a  part 
of  the  anterior  fossa  of  the  cranium.  Hold  them  to  the  light,  and  observe 
how  thin  they  are.  In  extreme  old  age,  when  the  diploe  of  the  skull 
becomes  absorbed,  the  orbital  plates  have  sometimes  large  holes  in  them. 
At  any  time  of  life  their  thinness  renders  them  liable  to  be  perforated 
by  sharp  instruments  thrust  into  the  orbit.  Wounds  of  the  brain  from 
such  accidents  are  sometimes  met  with.  Sir  C.  Bell  speaks  of  a  young 
man  having  been  killed  by  the  thrust  of  a  foil  which  had  lost  its  guard, 
and  passed  through  the  orbital  plate  into  the  brain.  Their  '  cerebral  sur- 
face '  is  slightly  convex,  and  generally  ridged  and  furrowed  by  the  impres- 
sions of  the  brain.  The  orbital  plates  of  the  frontal  bone  are  more  or 
less  arched  in  different  skulls.  Of  course  the  more  they  are  arched  the 
more  they  encroach  on  the  cranial  space,  and  therefore  the  less  room 
there  is  for  the  anterior  lobes  of  the  brain.  Contrast  the  skull  of  a 
monkey  with  that  of  a  man,  and  you  will  observe  a  marked  difference. 
Their  lower  surface  is  concave,  more  especially  near  the  external  angular 


FRONTAL     BONE.  45 

process,  where  there  is  a  depression  ('  lachrymal  fossa')  which  lodges  the 
lachrymal  gland.  Again,  near  the  internal  angular  process  there  is  a 
trace  of  a  slight  depression,  indicating  the  attachment  of  the  cartilagi- 
nous pulley  of  the  '  superior  oblique '  muscle  of  the  eye. 

Ethmoidal  Notch.— The  orbital  plates  are  separated  by  a  wide  gap, 
called  the  '  ethmoidal  notch/  because  it  receives  the  cribriform  plate  of 
the  ethmoid  bone,  which  here  fits  into  the  base  of  the  skull.  (Plate 
XIX.)  On  each  side  of  the  irregular  margins  of  the  notch  observe  the 
incomplete  cells  with  thin  walls.  These  cells  correspond  with,  and  are 
closed  by,  the  ethmoidal  ceUs  (Plate  XL  Fig.  2).  The  largest  ceU  of  all 
is  in  the  front;  and  this,  as  seen  in  Plate  VII.  Fig.  2,  leads  into  the 
frontal  sinus.  All  of  them  are  filled  with  air,  and  lined  by  mucous  mem- 
brane continuous  with  that  of  the  nose.  At  the  front  part  of  the  notch 
is  the  '  nasal  spine '  of  the  frontal  bone.  This  little  perpendicular  pro- 
jection— generally  broken  off  in  taking  the  skull  to  pieces — supports  the 
proper  nasal  bones  (Plate  XXIII.  Fig.  1),  and  helps  to  form  the  septum 
of  the  nose,  by  uniting  with  the  perpendicular  plate  of  the  ethmoid  bone. 
On  either  side  of  it  is  a  little  groove  which  forms  part  of  the  roof  of  the 
nose  (Plate  VIL  Fig.  1).  Immediately  in  front  of  the  nasal  spine  is  the 
jagged  surface  which  receives  the  nasal  bones,  and  the  nasal  process  of 
the  superior  maxillary  bone  (Plate  XVI.  Fig.  2).  Lastly,  on  the  margin 
of  the  ethmoidal  notch,  notice  two  grooves  which,  with  the  ethmoid 
bone,  form  the  '  anterior  and  posterior  ethmoidal  foramina/  The  anterior 
transmits  the  '  nasal '  branch  of  the  ophthalmic  division  of  the  fifth  nerve, 
and  the  anterior  ethmoidal  artery  and  vein;  the  posterior,  the  posterior 
ethmoidal  artery  and  vein. 

Connections. — The  frontal  is  connected  with  twelve  bones,  of  which 
two,  the  sphenoid  and  ethmoid,  are  single.  It  is  united  to  the  two  parietal 
bones  by  the  '  fronto-parietal '  or  '  coronal  suture '  (Plate  XVIII.  Fig.  2). 
Concerning  this  suture,  see  how  admirably  it  locks  the  bones  together, 
and  secures  the  arch  of  the  skull.  The  margin  of  the  frontal  bone  is 
bevelled  at  the  expense  of  its  inner  table  above,  of  its  outer  table  below; 
and  the  parietal  bone  is  adapted  accordingly.  The  lower  half  of  its  tem- 
poral margin  unites  with  the  greater  wing  of  the  sphenoid.  Its  external 
angular  process  is  connected  to  the  malar  bone;  its  internal  angular  pro- 
cess, to  the  nasal  bone  and  nasal  process  of  the  superior  maxillary.  Its 
orbital  plate  is  connected  to  the  sphenoid,  ethmoid,  and  lachrymal  bones. 
Look  well  into  the  orbits  and  see  these  several  connections.  They  form 


46  HUMAN    OSTEOLOGY. 

a  continuous  suture  from  one  external  angular  process  to  the  other. 
This  is  called  the  'transverse  frontal  suture.' 

Ossification. — The  frontal  bone  is  developed  from  two  centres, 
which  appear  one  on  each  side,  in  the  situation  of  the  frontal  eminence, 
about  the  seventh  week  of  foetal  life.  These  lateral  halves  meet  and 
form  a  vertical  suture  down  the  middle  of  the  forehead,  termed  the 
'  frontal '  suture;  so  that  in  children  the  two  halves  of  the  bone  are  easily 
separated.  Generally  this  suture  becomes  obliterated  during  the  second 
year;  but  sometimes  traces  of  it  persist,  as  seen  in  the  skull,  Plate  XVIII. ; 
hence  the  practical  rule  not  to  mistake  it  for  a  fracture.81 

The  frontal  bone  gives  attachment  to  three  muscles;  namely,  to  part 
of  the  '  temporal,'  part  of  the  '  orbicularis  oculi,'  and  the  '  corru gator 
supercilii.' 

Comparative  Osteology. — In  some  animals,  such  as  the  Carnivora 
(see  skull  of  tiger)  the  temporal  muscle  extends  so  far  forward  that  there 
is  no  room  for  articulation  between  the  malar  bone  and  the  external  angu- 
lar process  of  the  frontal.  Thus,  in  these  skulls  the  temporal  fossa  and 
the  orbit  are  not  separated  by  bone  as  in  man.  This  character  runs 
throughout  the  Carnivora,  Rodentia,  Edentata,  and  Pachydermata.  In 
some  animals  the  air  cells  are  very  numerous  and  large.  Let  any  one 
who,  admiring  the  intelligence  of  the  elephant,  imagines  him  to  have  a 
huge  brain,  put  his  hand  into  the  foramen  magnum  of  the  skull  which 
stands  on  the  pedestal  in  the  Mus.  Eoy.  Coll.  Surg.  and  explore  the  cranial 
cavity.  He  will  find  that  this  forms  but  a  small  portion  of  the  size  of 
the  head.  And  now  looking  at  the  sections  of  the  skulls  in  the  case  be- 
hind it,  he  will  see  that  the  larger  part  of  the  skull  is  formed  by  cells  or 
air  spaces  between  the  tables  of  the  frontal,  parietal,  and  occipital  bones, 
which  often  separate  the  inner  and  outer  tables  of  the  skull  to  the  extent 
of  a  foot.  These  m  ke  a  vast  increase  in  the  size  of  the  skull — an  increase 
of  advantage,  however,  i.s  it  affords  additional  leverage  for  those  muscles 
which  are  inserted  into  the  back  of  the  skull,  and  raise  the  massive  head, 
including  the  trunk,  tusks,  and  jaws.  The  place  to  aim  at  in  this 
animal  is  just  above  the  root  of  the  trunk,  where  the  case  of  the  brain  is 
not  much  thicker  than  a  shilling.  These  sinuses  are  also  well  developed 
in  the  owl  and  the  giraffe.  In  the  great  extinct  sloths  the  upper,  back, 

31  Dr.  Leach  and  others,  who  have  examined  the  immense  collection  of  crania  in 
the  Catacombs  at  Paris,  have  remarked  that  the  number  of  adult  skulls  in  which  the 
frontal  suture  remained  unobliterated  was  about  one  in  eleven. 


PLATE  VIII. 


IVL-astoid 
portion 


"Kastoid 
foramen 


icjuamous  portion, 


Zygoma.  . 
Tubercle  at 


Di^astricus 
Mas  tend  process 


IpT.       fJ"*  Eminent^.  articularis. 
Glenoid  cavity. 
rlenoifl  fi&gure  . 


Vaginal  process 


portion. 
J/leatus  au<3litorius  externus. 

Styloid  process. 


Middlle 

Zygoma 

3up^  Petrosa\  einug 
Mfatus  auditorvus  inter PU 
Carotid 


TEMPORAL    BONE.  47 

and  side  walls  of  the  cranium  were  thus  inflated  with  air;  so  that  in  these 
instances  the  brain  is  protected  by  a  double  skull,  with  air  between  the 
two.  This  modification  not  only  lightened  the  skull,  but  protected  the 
brain  from  the  falling  trees  uprooted  for  food  by  these  animals. 

The  horns  of  animals  such  as  oxen,  sheep,  and  antelopes,  consist  of  a 
horny  sheath  supported  upon  a  long  mass  of  bone  which  grows  from  the 
surface  of  the  frontal  bone.  These  horns  last  the  lifetime  of  the  animal, 
excepting,  indeed,  in  the  case  of  the  prong-horned  antelope  at  the  Zoo- 
logical Gardens,  which  has  twice  shed  its  horns  (No.  3713).  The  antlers  of 
the  deer  consist  entirely  of  bone,  and  grow  from  a  projection  on  the 
frontal  bone,  and  are  shed  annually;  even  the  Wapiti  deer  sheds  its  huge 
antlers  every  year,  and  the  extinct  Irish  elk  formed  no  exception  to  this 
rule.  Antlers  are  very  vascular,  and  are  covered  by  a  vascular  membrane, 
termed  the  '  velvet/  until  the  full  growth,  when  they  lose  the  '  velvet/ 
and  are  themselves  ultimately  shed.  The  horn  of  the  rhinoceros  is  simply 
horny,  and  has  no  shaft  of  bone  in  its  interior. 


TEMPOKAL  BONE. 

(PLATE  VIII.) 

Three  Parts. — This  bone  occupies  the  temples.  It  is  a  complicated 
bone,  even  on  the  surface;  much  more  so  in  its  interior,  because  it  includes 
the  organ  of  hearing.  It  consists  of  three  parts, — a  squamous  portion, 
situated  in  the  temple;  a  mastoid,  forming  the  little  projection  behind 
the  ear;  and  a,  petrous,  which  contains  the  organ  of  hearing,  and  projects 
like  a  wedge  into  the  base  of  the  skull.  This  division  is  very  convenient: 
but  the  natural  divisions  of  the  bone  are — 1.  The  squamous;  2.  the 
periotic,  comprising  the  petrous  and  mastoid;  and,  3,  the  tympanic,  or 
small  ring  of  bone  .which  surrounds  the  membrana  tympani,  and  by  its 
outward  growth  comes  to  form  the  external  auditory  passage.  These 
parts  are  separate  in  the  human  foetus,  and  permanently  so  in  many  of 
the  lower  animals. 

Squamous  Portion. — The  squamous  portion,  named  from  its  scale- 
like  appearance,  forms  part  of  the  wall  of  the  temple.  It  is  very  thin; 
hence  the  danger  of  a  blow  here.  Its  smooth  outer  surface  is  entirely 
covered  by  the  temporal  muscle,  to  which  it  gives  origin.  Its  inner  sur- 


48  HUMAN    OSTEOLOGY. 

face  is  marked  by  the  convolutions  of  the  brain,  and  by  a  narrow  groove 
which  sweeps,  in  a  curved  direction,  from  before  backward,  indicating 
the  course  of  the  posterior  branch  of  the  middle  meningeal  artery.  (Plate 
VIII.  Fig.  2.) 

Zygoma.. — At  the  lowei  part  of  the  squamous  portion  there  is  an  out- 
growth of  bone,  termed  the  '  zygoma'  (^vycoj^a,  a  bolt  or  bar).  It  pro- 
jects horizontally  forward,  and  can  be  easily  felt  on  the  side  of  the  face. 
It  is  connected  by  a  strongly  serrated  suture  with  a  similar  projection 
from  the  malar  bone;  so  that  the  two  together  form  an  arch  ('  zygomatic 
arch')  beneath  which  the  temporal  muscle  plays.  (Plate  XV.  Fig.  2.) 
The  base  of  the  zygoma  is  very  broad,  and  appears  to  spring  from  two 
roots, — an  anterior  and  a  posterior:  in  the  space  between  them  is  the 
'  glenoid  cavity/  which  forms  the  socket  for  the  lower  jaw.  The  poste- 
rior root  (supra-mastoid  ridge)  runs  backward  in  the  same  line  with  the 
zygoma,  and  forms  the  upper  boundary  of  the  glenoid  cavity:  after  that, 
it  passes  over  the  meatus  auditorius  externus,  and  then  it  gradually  fades 
away,  marking  the  line  of  separation  between  the  squamous  and  the 
mastoid  divisions  of  the  bone.  In  the  negro  race,  this  supramastoid  ridge 
is  strongly  marked,  and  is  characteristic  of  a  degraded  type  of  skull  (see 
two  Tasmanian  skulls,  Nor.  Hum.  Ost.  Nos.  1096-1097).  The  anterior 
is  the  main  root;  it  is  very  broad  and  strong,  runs  transversely  inward 
and  forms  the  front  boundary  of  the  glenoid  cavity.  It  is  called  the  '  emi- 
nentia  articularis.'  This  is  crusted  with  cartilage  in  the  recent  state,  and 
forms  additional  surf  ace  for  the  play  of  the  lower  jaw.  Under  ordinary 
circumstances,  the  'condyle'  of  the  jaw  is  in  the  glenoid  cavity;  but 
while  the  mouth  is  opening  widely,  the  condyle  can  be  felt  sliding  so  far 
forward  that  the  finger  can  be  placed  into  the  socket  behind  it.  In  fits 
of  laughter  or  of  yawning,  the  condyles  may  be  suddenly  dragged  in  front 
of  the  articular  eminences  by  the  muscles;  and  then  the  jaw  is  dislocated 
into  the  zygomatic  fossa.  Under  such  circumstances  a  person  presents  a 
very  ridiculous  appearance,  since  the  mouth  remains  wide  open  until  the 
dislocation  is  reduced.  At  the  base  of  the  zygoma  we  notice  a  little 
tubercle  ('tubercle  of  the  zygoma'),  to  which  is  attached  the  external 
lateral  ligament  of  the  lower  jaw.  Lastly,  the  upper  edge  of  the  zygo- 
ma gives  attachment  to  the  temporal  aponeurosis;  the  lower  edge  gives 
origin  to  the  masseter  muscle. 

Glenoid  Cavity. — The  '  glenoid  cavity '  (yXijvt?,  a  socket),  or  socket 
for  the  lower  jaw,  is  concave  and  oval,  with  the  long  diameter  transverse, 


TEMPORAL    BONE.  49 

or  nearly  so.  At  the  bottom  of  it  notice  a  fissure,  termed  the  '  fissura 
Glaseri/  or  '  glenoid  fissure/  the  remains  of  the  original  separation  be- 
tween the  squamous  and  tympanic  portions  of  the  bone.  The  part  in 
front  of  the  fissure  is  the  socket  for  the  jaw:  the  part  behind  it  is  occu- 
pied by  a  lobe  of  the  parotid  salivary  gland.  Pass  a  bristle  up  the  fissure, 
to  see  that  it  leads  to  the  tympanum  of  the  ear.  The  glenoid  fissure  con- 
tains the  '  processus  gracilis '  of  the  '  malleus/  the  tympanic  artery,  the 
'  laxator  tympani '  muscle,  and  is  usually  said  to  transmit  the  '  chorda 
tympani '  nerve;  but  this  nerve,  strictly  speaking,  runs  through  a  little 
canal,  close  by  the  fissure  termed  '  Canal  of  Huguier/  Between  the 
glenoid  cavity  and  the  meatus  auditorius  there  is  a  slight  process  which 
affords  support  to  the  lower  jaw,  and  guards  against  dislocation  backward. 
This  '  postglenoid  process '  is  generally  well  marked  in  African  skulls,  and 
always  so  in  the  gorilla,  the  animal  which  approaches  man  so  nearly. 

Mastoid  Portion. — The  '  mastoid  portion '  forms  the  prominence  of 
bone  which  is  felt  behind  the  ear  termed  the  mastoid  '  process '  (ftaffrds, 
a  nipple).     This  process  gives  insertion  and  great  leverage  to  some  of  the 
muscles  which  move  the  head  round,  viz.  the  '  sterno-cleido-mastoideus/ 
under  that  the  '  splenius  capitis/  and  still  deeper  the  '  trachelo-mastoid/ 
Beneath  all  these  muscles  the  occipital  artery  runs  to  the  back  of  the 
head,  along  a  slight  groove  in  the  bone,  internal  to  the  digastric  fossa. 
These  muscles,  as  seen  in  Plate  VIII.  Fig.  1,  are  also  inserted  into  the 
rough  surface  above  and  behind  the  mastoid  process.     If  a  section  be 
made  through  the  process,  it  is  found  to  contain  large  and  freely  commu- 
nicating cells,  termed  '  mastoid/  which  open  into  the  back  part  of  the 
tympanum.     These  cells,  like  the  tympanum  itself,   contain  warm  air, 
which  is  admitted  from  the  back  part  of  the  nostrils  through  '  the  Eusta- 
chian  tube/    They  not  only  make  the  bone  light,  but  are  useful  to  the 
sense  of  hearing,  by  allowing  more  space  for  the  vibration  of  the  air. 
Like  the  frontal  cells,  and  indeed  all  the  air-cells  in  the  bones  of  the  skull, 
they  are  not  developed  till  the  approach  of  puberty.     In  cases  of  deaf- 
ness, arising  from  obliteration  of  the  Eustachian  tube,  it  was  formerly 
the  practice  to  make  an  opening  into  the  mastoid  cells,  in  order  to  admit 
free  access  of  air  into  the  tympanum.    The  success  attending  this  proceed- 
ing induced  Just  Berger,  physician  to  the  King  of  Denmark,  to  have  the 
operation  done  upon  himself;  but  he  died  twelve  days  afterward  from  ex- 
tension of  inflammation  to  the  membranes  of  the  brain;  and  the  death  of 
this  illustrious  man  brought  the  operation  into  disrepute.     Internal  to  the 


50  HUMAN   OSTEOLOGY. 

mastoid  process  is  a  deep  fossa,  termed  the  '  digastric  fossa/  where  the 
'digastric '  muscle  arises.  Behind  the  process  is  a  hole,  called  the  '  mastoid 
foramen/  through  which  a  vein  runs  from  the  lateral  sinus  to  the  outside 
•of  the  head.  This  explains  why  leeches,  applied  behind  the  ears,  relieve 
•congestion  of  the  brain.  Lastly,  on  the  cerebral  aspect  of  the  mastoid 
portion,  notice  the  'groove  for  the  lateral  sinus/ 

Petrous  Portion.— The  '  petrous  portion '  derives  its  name  from  the 
hardness  of  its  constituent  bone  (nerpos,  a  rock).  It  projects  horizontally 
into  the  base  of  the  skull  (Plate  XIX.),  and  so  carries  far  out  of  harm's 
way  the  delicate  organ  of  hearing  which  it  contains.  Its  shape  is  like  a  tri- 
angular pyramid  with  the  apex  inward;  so  that,  for  descriptive  purposes, 
it  may  conveniently  be  divided  into  three  surfaces — an  anterior,  a  posterior, 
and  an  inferior:  then  there  is  a  base  and  an  apex.  Our  best  plan  is  to 
examine  each  of  these  parts  separately,  that  we  may  be  able  to  answer  the 
question,  what  is  seen  on  the  anterior,  what  on  the  posterior  surface, 
and  so  forth.  Take  the  base  first. 

Meatus  Auditorius  Externus. — At  the  base  of  the  petrous  portion 
is  the  orifice  of  the  passage  to  the  ear,  termed  the  '  meatus  auditorius 
externus/  It  is  situated  immediately  behind  the  glenoid  cavity,  and  its 
boundaries  are  chiefly  formed  by  a  curved  plate  of  bone,  called  the  '  pro- 
cessus  auditorius.'  Observe,  first,  that  the  edge  of  it  is  very  jagged,  for 
the  attachment  of  the  cartilage  of  the  ear;  and  then  look  carefully  down 
the  passage  to  see  that  this  curved  plate  of  bone  forms  its  boundary  wall 
all  round,  except  at  the  uppermost  part.  This  inspection  will  probably 
suggest  that  the  whole  plate  is  something  superadded  to  the  rest  of  the 
bone, — a  sort  of  after-growth;  which  is  precisely  the  case.  In  the  foetus 
there  is  no  meatus,  but  simply  a  ring  of  bone  forming  three-fourths  of 
a  circle,  the  deficiency  being  at  the  upper  part.  This  ring  is  ossified 
independently  about  the  third  month,  is  quite  distinct  from  the  other 
parts,  and  to  it  is  attached  the  membrane  of  the  drum  of  the  ear  (membrana 
tympani) ;  so  that  at  this  early  period  it  might  be  rudely  compared  to  a 
hoop  with  a  membrane  stretched  across  it.  In  many  animals  this  remains 
permanently  a  distinct  bone,  under  the  name  of  the  'tympanic  bone/ 
(Plate  XVIII.  Fig.  5.)  In  process  of  time,  however,  the  hoop  begins  to 
grow  out  on  its  external  side,  and  thus  becomes  a  canal  or  meatus,  which, 
as  it  grows  longer,  gradually  coalesces  with  the  other  constituents  of  the 
bone. 

Respecting  the  shape  of  the  passage,  observe  that  it  is  oval,  with  the 


^.-Ca-nal  ftr  Tensor  ty  mpani. 

.look "here  Foi~ ^r i*roces?«s  Cochleari  fbrmia 

""'••Eustachian  tube. 


Gleuoi<i  cavity 

Glenoid  fissure  .... 


....'.'••Garoticl  canal. 


...Aqueiluctus  cocVJeae. 
Foramen PorJacot>son's  T\erye. 
...Jugular  Eossa. 

Foramen  for  A.rnoV4's  ner vt . 

Stylo -masto'id  foraTnen . 

....  ..Groove  For  occipital  artery. 

Digastric  fossa*. 

Maatoid  foramen. 


TEMPORAL  BOME. 


Groove  for  middle 
>wetimgesLl  artery. 


Depression.  Fo- 
Gaisser  wn.  b&rt^V 


SupTPe.Vposal  aiutrc 


TEMPORAL    BONE.  51 

long  diameter  nearly  vertical;  therefore  all  specula  used  for  examining 
the  ear  ought  to  be  of  the  like  shape.  The  narrowest  part  of  the  passage, 
in  the  recent  state,  is  about  the  middle;  hence  if  a  foreign  body,  such  as 
a  pea,  happen  to  get  into  the  ear,  it  is  generally  pushed  through  the  nar- 
row part  by  clumsy  efforts  to  extract  it,  and  then  the  moisture  of  the  ear 
causes  it  to  swell,  and  makes  its  extraction  most  difficult  and  painful.  A 
boy,  eight  years  of  age,  had  a  grain  of  Indian  corn  thrust  into  his  ear  by 
one  of  his  schoolfellows.  The  schoolmaster,  in  his  wisdom,  endeavored 
to  remove  it  by  attaching  a  piece  of  wax  to  the  end  of  a  stick,  and  thrust- 
ing it  into  the  passage.  Four  days  afterward,  the  boy  was  brought,  with 
his  ear  in  a  state  of  acute  inflammation,  to  the  doctor,  who  eventually 
succeeded  in  extracting  the  grain  by  means  of  a  '  curette,'  with  the  point 
bent  to  a  right  angle.  The  grain  of  corn  had  increased  to  one-third  more 
than  its  natural  size." 

Petrous  Portion:  Anterior  Surface. — The  anterior  surface  (Plate 
IX.  Fig.  2)  of  the  petrous  portion  forms  part  of  the  middle  cerebral  fossa 
which  lodges  the  middle  lobe  of  the  brain,  and  bears  more  or  less  marks 
corresponding  to  the  convolutions.  About  the  middle  of  it  is  a  little  emi- 
nence, indicating  the  position  of  the  '  superior  semicircular  canal '  (a  part 
of  the  internal  ear).  More  forward,  is  a  small  furrow  leading  to  an  open- 
ing termed  the  '  hiatus  Fallopii/  which  transmits  the  '  great  petrosal ' 
nerve.  Immediately  to  the  outer  side  of  this  is  a  smaller  furrow  and 
opening,  which  gives  passage  to  the  'lesser  petrosal  nerve/  Near  the 
apex  is  a  depression  for  the  'Gasserian  ganglion/  External  to  this  is  the 
termination  of  the  '  carotid  canal/  Lastly,  at  the  angle  where  the  squa- 
mous  and  petrous  portions  meet  (Plate  IX.  Fig.  1),  you  will  observe  two 
tubes  running  backward  parallel  to  each  other,  like  a  double-barrelled  gun 
(except  that  they  lie  one  above  the  other):  they  both  lead  to  the  tympa- 
num. The  upper  of  the  two  is  the  canal  for  the  '  tensor  tympani '  muscle; 
the  lower,  which  is  by  far  the  larger,  is  the  Eustachian  tube,  or  passage 
which  conducts  the  air  from  the  pharynx  to  the  tympanum.  The  thin 
partition  separating  the  two  barrels  is  called  the  'processus  cochleari- 
formis/ 

Petrous  Portion:  Posterior  Surface. — The  posterior  surface  of 

the  petrous  portion  forms  part  of  the  posterior  fossa  of  the  base  of  the 

skull.  (Plate  XIX.)     The  most  prominent  object  upon  it  is  the  'meatus 

auditorius  internus'  (Plate  VIII.  Fig.  2),  a  large  canal  which  runs  nearly 

**  '  Aural  Surgery, '  p.  179.     Mr.  Wilde. 


52  HUMAN   OSTEOLOGY. 

horizontally  outward,  and  transmits  the  '  seventh  pair '  of  nerves,  consist- 
ing of  the  auditory  nerve  (portio  mollis),  and  the  motor  nerve  of  the  face 
(portio  dura).  It  also  transmits  the  auditory  artery,  a  branch  of  the 
basilar.  The  meatus  is  much  larger  than  the  nerves  which  it  transmits, 
the  space  between  them  and  the  bony  canal  being  filled  by  a  fluid  (cere- 
bro-spinal),  which  surrounds  and  supports  the  brain.  In  fractures  through 
the  base  of  the  skull  involving  the  meatus,  the  fluid  sometimes  oozes  out 
through  the  external  ear:  this,  therefore,  is  regarded  as  a  very  grave 
symptom  in  cases  of  injuries  to  the  head.  A  transverse  section  near  the 
bottom  of  the  meatus  would  show  that  it  is  divided  by  a  small  ridge  of 
bone  into  two  unequal  parts,  as  seen  in  Fig.  13.  In  the  upper  and  smaller 
of  the  two  is  the  commencement  of  a  special  canal  (aquaeductus  Fallopii) 
for  the  motor  nerve  of  the  face;  in  the  lower  there  are  several  minute 
apertures  arranged  in  a  spiral  form  (lamina  cribrosa),  through  which  the 

Aquseductus  Fallopii. 
Ridge  of  bone. 


Lamina  cribrosa,  through  which  the  nerves  pass 
to  tJie  cochlea. 


Fro.  13. 

fibres  of  the  auditory  nerve  reach  the  internal  ear.  About  a  quarter  of  an 
inch  behind  the  meatus  is  a  slit-like  opening  which  looks  backward,  and 
is  termed  the  '  aquwductus  vestibuli.'  This,  though  about  a  quarter  of 
an  inch  long,  soon  contracts  so  much  that  it  will  barely  admit  a  bristle. 
It  leads  to  the  vestibule  of  the  internal  ear.  Immediately  below  the 
meatus  there  is  a  conical  pit,  which  is  wide  at  first,  but  gradually  con- 
tracts to  a  minute  canal,  leading  to  the  cochlea,  termed  the  '  aqueeductus 
cochkce.'  These  minute  '  aqueducts '  leading  to  the  internal  ear  sometimes 
transmit  small  blood-vessels. 

Petrous  Portion:  Inferior  Surface. — The  inferior  surface  of  the 
petrous  portion  presents  an  irregular  aspect,  and  has  many  holes  in  it 
(Plate  IX.  Fig.  1).  Beginning  near  the  base,  notice,  first,  the  '  styloid 
process/  so  called  from  its  resemblance  to  an  ancient  *  style,'  or  pen.  It 
is,  originally,  distinct  from  the  rest  of  the  bone,  but  gradually  coalesces 


TEMPORAL    BONE.  53 

with  it  at  the  end  of  the  third  year.  This  long  *  process '  descends  with  a 
slight  inclination  forward,  and  gradually  tapers  to  a  sharp  point.  Its 
length  varies  in  different  skulls;  generally  it  is  about  half  an  inch  long. 
In  old  skulls  it  is  sometimes  longer:  there  is  a  skull  in  the  Museum  of  St. 
Bartholomew's  Hospital  which  has  a  styloid  process  three  inches  long.  It 
gives  origin  to  three  muscles  and  two  ligaments.  The  muscles  are  for 
the  movement  of  the  tongue  and  pharynx;  they  arise  as  follows: — the 
'  stylo-pharyngeus,'  from  the  inner  side  of  the  base;  the  *  stylo-hyoideus/ 
from  the  middle  and  outer  aspect;  and  the  '  stylo-glossus/  from  the  front 
of  the  process  (Plate  VIII.  Fig.  1).  To  the  tip  itself  is  attached  the 
'  stylo-hyoid  ligament/  which  runs  downward  and  forward  to  the  lesser 
cornu  of  the  os  hyoides.  The  styloid  process  is  nothing  more  than  ossifi- 
cation of  part  of  this  ligament.  The  other  ligament  attached  to  the  pro- 
cess is  the  '  stylo-maxillary/  which  separates  the  submaxillary  from  the 
parotid  gland.  Lastly,  the  fore  part  of  the  root  of  the  styloid  process  is 
surrounded  by  a  kind  of  bony  sheath,  termed  the  '  vaginal  process,'  about 
which  there  is  nothing  to  be  remarked  except  that  it  is  a  continuation  of 
the  plate  of  bone  which  forms  the  hinder  part  of  the  glenoid  cavity. 

Between  the  mastoid  and  styloid  processes  is  a  hole  termed  the  *  stylo- 
mastoid  foramen/  (Plate  IX.  Fig.  1.)  It  gives  exit  to  the  motor  nerve 
of  the  face  (portio  dura),  which  entered  the  bone  at  the  meatus  audi- 
torius  internus.  The  stylo-mastoid  artery,  a  branch  of  the  posterior  auri- 
cular, enters  at  this  foramen,  and  supplies  the  tympanum.  If  you  intro- 
duce a  stiff  bristle  into  the  hole,  you  will  probably  succeed  in  passing  it 
through  the  bony  canal  traversed  by  the  nerve  from  its  entrance  to  its 
exit.  The  canal  is  a  complete  tube  of  bone,  called  the  'aquaeductus 
Fallopii ' "  after  the  anatomist  who  first  described  it.  (Plate  LIX.)  The 
passage  of  this  nerve  through  the  temporal  bone  renders  it  liable  to  be 
injured  in  fractures  of  the  base  of  the  skull,  or  in  disease  of  the  ear; 
and  this  explains  the  paralysis  of  one  side  of  the  face  which  sometimes 
occurs  under  these  circumstances. 

On  the  inner  side  of  the  stylo-mastoid  foramen  is  a  deep  depression 
termed  the  '  jugular  fossa.'  This,  with  a  corresponding  part  of  the  occi- 
pital bone,  forms  the  '  foramen  lacerum  posterius.'  (Plate  XX.)  Here  the 
lateral  sinus  pours  its  blood  into  the  commencement  of  the  internal  jugu- 
lar vein,  which  forms  a  great  bulge  and  fills  the  fossa.  Here  also  the 
eighth  pair  of  nerves  leaves  the  skull  (through  a  little  notch  in  the  front 
33  Fallopius  was  a  distinguished  Italian  anatomist,  born  1523,  died  1563, 


54  HUMAN   OSTEOLOGY. 

part  of  the  foramen  lacerum) ;  and  here,  one  of  the  posterior  meningeal 
arteries,  a  branch  of  the  occipital,  enters  it.  On  the  outer  wall  of  the 
jugular  fossa,  near  the  root  of  the  styloid  process,  we  find  the  minute 
foramen  which  transmits  the  auricular  branch  of  the  pneumogastric 
nerve.  In  front  of  the  jugular  fossa  is  the  large  circular  commencement 
of  the  canal  in  the  petrous  bone,  through  which  the  carotid  artery  enters 
the  skull  ('carotid  canaF).  The  canal  mounts  nearly  perpendicularly 
for  a  short  distance,  and  then,  turning  forward  and  upward,  emerges  at 
the  apex  of  the  bone.  On  the  plate  of  bone  which  separates  the  jugular 
fossa  from  the  carotid  canal,  there  is  a  minute  foramen  which  transmits 
the  tympanic  branch  of  the  glosso-pharyngeal  nerve. S4  Near  the  apex  is 
a  rough  surface  which  gives  origin  to  the  '  tensor  tympani '  and  '  levator 
palati '  muscles.  The  apex  itself  presents  nothing  more  than  the  termi- 
nation of  the  carotid  canal,  and  helps  to  form  one  of  the  boundaries  of 
the  jagged  hole  at  the  base  of  the  skull,  termed  the  '  foramen  lacerum  me- 
dium.' (Plate  XX.) 

Along  the  sharp  border  between  the  anterior  and  posterior  surfaces  of 
the  petrous  portion  remark  the  groove  for  the  '  superior  petrosal  sinus/ 
which  discharges  itself  into  the  lateral  sinus.  The  faintly  indicated 
groove  along  the  fore  part  of  the  lower  border  of  the  posterior  surface  is 
for  the  '  inferior  petrosal  sinus/  The  nearness  of  these  venous  chan- 
nels to  the  cavity  of  the  tympanum  explains  the  bleeding  from  the  ear 
which  sometimes  occurs  in  fractures  running  through  the  petrous  portion 
of  the  temporal  bone. 

Connections. — The  temporal  is  connected  with  five  bones.  The 
squamous  portion  is  connected  to  the  parietal  bone  and  the  great  Aving  of 
the  sphenoid  bone  by  the  '  temporo-parietal '  and  '  temporo-sphenoidal ' 
sutures,  concerning  which  the  following  mechanism  must  be  noticed; 
namely,  that  the  squamous  part  overlaps  the  parietal  above,  but  is  itself 
overlapped  by  the  sphenoid  below — an  arrangement  which  greatly  con- 
tributes to  the  security  of  the  arch  of  the  skull.  The  mastoid  part  is 
connected,  above,  to  the  posterior  inferior  angle  of  the  parietal  by 
the  '  masto-parietal '  suture,  and,  behind,  to  the  occipital  by  the 
'  masto-occipitaP  suture.  The  petrous  part  is  wedged  into  the  base  of 
the  skull  between  the  sphenoid  and  occipital  bones.  (Plate  XIX.)  The 
zygomatic  process  is  connected  to  the  malar  bone  by  a  strong  suture,  the 

34  Arnold's  nerve  is  the  auricular  branch  of  the  pneumogastric;  Jacobson's  nerve 
is  the  tympanic  branch  of  the  glosso-pharyngeal. 


TEMPORAL    BONE.  55 

*  zygomatic/  which  slopes  downward  and  backward.  Lastly,  the  glenoid 
cavity  articulates  with  one  of  the  condyles  of  the  lower  jaw.  In  the 
living  subject,  an  inter-articular  fibro-cartilage,  lined  above  and  below  by 
synovial  membrane,  separates  the  two  articular  surfaces,  and  protects  this 
part  of  the  skull  from  the  effects  of  a  blow  under  the  lower  jaw. 

Ossification. — The  temporal  bone  is  developed  from  four  centres  of 
ossification;  namely,  one  for  each  of  the  following  parts: — the  squamous, 
including  the  zygoma;  the  petrous  and  mastoid,  or  periotic  bone;  the 
tympanic  or  processus  auditorius;  and  lastly,  the  styloid  process.  Some 
of  these  remain  permanently  distinct  bones  in  many  of  the  lower  animals; 
and  it  is  worthy  of  remark,  that  even  in  the  human  subject  traces  of  the 
union  of  all  are  visible  even  in  advanced  age.  The  most  curious  develop- 
ment is  that  of  the  tympanic  part;  it  is  a  simple  ring  of  bone  in  the 
foetus,  grooved  inside  for  the  attachment  of  the  membrana  tympani,  which 
eventually  grows  out  so  as  to  form  the  meatus  auditorius.  (Nor.  Hum. 
Ost.  Nos.  34  and  43.)  In  the  foetus,  the  mastoid  part  is  very  small,  and 
gradually  enlarges  toward  puberty  by  the  formation  of  the  mastoid  cells. 
The  styloid  part  is  for  a  long  time  cartilaginous  after  birth,  and  ossifies 
slowly  with  age.  The  ossification  of  the  squamous  part  commences  about 
the  eighth  week  of  foetal  life;  of  the  petrous  and  mastoid,  between  the 
fifth  and  sixth  months;  of  the  tympanic  ring,  about  the  third  month;  of 
the  styloid  process,  after  puberty. 

Right  or  Left  ? — The  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body  if  he  hold  the  petrous  portion  (on 
which  part  of  the  brain  lies)  inward ;  the  zygoma  (which  articulates  with 
tke  malar)  forward,  and  the  glenoid  cavity  downward. 

Comparative  Osteology. — In  white  men  the  temporal  bone  very 
rarely  articulates  with  the  frontal,  but  this  abnormality  appears  to  be  less 
rare  in  some  colored  races.  In  the  Hum.  Ost.  Ser.  it  may  be  seen  in  four 
skulls  of  natives  of  New  Caledonia,  Nos.  1159, 1160,  1161  and  1146;  in 
two  Australian  skulls,  Nos.  1088,  1071,  as  well  as  in  two  remarkably  long 
skulls  in  the  General  Ost.  Ser.  Nos.  126,  127.  Some  of  these  abnormali- 
ties may  be  explained,  by  referring  to  Plate  XVIII.  Fig.  5,  in  which  it 
will  be  seen  that  where  these  bones  meet,  is  the  anterior  lateral  fontanelle. 
Here  there  is  occasionally  developed  a  small  Wormian  bone  called  the 
'  Epipteric  bone/  (General  Ost.  Ser.  No.  116.)  If  the  epipteric  bone 
unite  to  either  the  sphenoid  or  parietal,  the  articulation  is  normal,  but 
if  to  the  frontal  or  temporal,  it  is  abnormal;  in  the  Orang  Outan  the 


56  HUMAN    OSTEOLOGY. 

temporal  bone  articulates  with  the  frontal  normally,  and  this  is  also  the 
case  in  nearly  all  the  monkeys. 

It  seems  curious  that  the  Howling  Monkey  (Mycetes  laniger)  has 
these  articulations  similar  to  those  of  man. 

Notice  the  immense  zygomatic  arch  in  the  skeleton  of  the  manatee. 
(No.  2647.) 

In  crocodiles  the  tympanic  cavity  is  completely  walled  in  by  bone;  so 
that  they  hear  by  vibrations  communicated  through  bony  substance. 

In  all  the  Mammalia,  and  in  them  alone,  the  lower  jaw  articulates 
directly  with  the  temporal  bone.  By  referring  to  No.  12  in  the  Nor. 
Hum.  Ost.  the  tympanic  bone  and  membrane  in  the  foetus  may  be  seen 
at  the  base  of  the  skull.  The  fissura  Glaseri  is  open  widely,  and  the 
processus  gracilis  of  the  malleus  lies  in  it.  In  all  Mammalia  the  malleus 
remains  very  small  and  becomes  cut  off  from  the  glenoid  cavity  by  the 
outgrowth  of  the  tympanic  bone;  but  in  birds  (see  Sep.  Ser.)  the  malleus 
becomes  largely  developed,  projects  between  the  squamous  and  tympanic 
bones,  and,  under  the  name  of  '  quadrate  bone/  comes  to  support  and 
form  the  articulation  for  the  lower  jaw. 


SPHENOID  BONE. 
(PLATES  X.,  XI.) 

Constituent  Parts. — The  sphenoid  bone  is  so  called  because  it  is 
wedged  in  at  the  base  of  the  skull  between  all  the  other  bones  of  the  cra- 
nium (0(prfv,  a  wedge,  eidos,  form).  As  it  not  only  enters  into  the  for- 
mation of  the  base  of  the  skull,  the  orbits,  the  temples,  and  the  nasal 
passages,  but  is  connected  with  all  the  bones  of  the  cranium,  and  many 
of  those  of  the  face,  one  cannot  be  surprised  that  it  is  a  difficult  bone  to 
understand.  Fortunately,  it  bears  a  remarkable  resemblance  to  a  bat 
with  extended  wings;  so  that  we  can  shape  our  description  accordingly. 
It  presents,  then — 1.  A  body,  or  central  part;  2.  The  two  greater  wings; 
3.  The  two  lesser  wings;  4.  The  pterygoid  processes,  which  make  the  two 
legs  of  the  bat.  -^ 

Body :  four  Surfaces.— Commencing  with  the  body,  we  must  ex- 
amine its  four  surfaces— a  '  superior,'  and  '  inferior/  an  '  anterior,'  and  a 
'posterior.' 


"PLATE  X. 


Sphenoid  Bone 

fossa  .Optic  fora* 

T3tW.aa.inn5 


c> 


mosum ii'.^S       jS^ 

Hr      )flH  I  Vainer 

F/ 

inous  pro  cess__^/        ^:: 
Ptery^oid  proces 


>ular  process 
Posterior  aspect 


Leva±or  pa.lj>e"braE.  Second  Vieacl  of  Bectus  extern'us. 


Bectus  sup? 
Obliquus  supT  _ 


lendon  common  to    __,      ^ 

..    T%3. 


rising  roxind  tlie  Foramen  optricum  . 


inferior 


to 


.ITotcnVor  Palabebone 

Hamukrrircceas 


Anterior  aspect. 


SPHENOID     BONE.  57 

The  superior  surface  of  the  body  (Plate  X.  Fig.  1)  comprises  what  is 
seen  of  the  body  on  the  inside  of  the  base  of  the  skull.  There  is  a  deep 
depression  in  it,  termed  the  'pituitary  fossa,' which  lodges  the  '  pituitary* 
body."  Another  name  given  to  it  is  the  *  sella  turcica,'  from  its  resem- 
blance to  a  Turkish  saddle.  In  front  of  it  is  an  eminence,  termed  the 
*  olivary  process,'  from  its  olive-like  shape.  This  process  supports  the  com- 
missure of  the  optic  nerve  which  makes  a  slight  transverse  groove  (the 
'  optic  groove ')  upon  it,  leading  on  each  side  to  the  '  optic  foramen ' 
through  which  the  nerve  enters  the  orbit.  In  front  of  the  olivary  process 
is  a  smooth  and  slightly  concave  surface,  which  supports  the  roots  of  the 
olfactory  bulbs,  and  terminates  in  the  middle  line  in  the  'ethmoidal 
spine/  which  articulates  with  the  ethmoid  bone. 

Each  side  of  the  '  body '  is  more  or  less  distinctly  marked  by  a  broad 
groove  which  winds  upward  in  a  gentle  curve,  and  lodges  the  internal 
carotid  artery  as  it  passes  through  the  *  cavernous  sinus '  after  entering 
the  skull;  generally,  a  little  tubercle,  called  the  'middle  clinoid  process,' 
rises  from  the  side  of  the  groove.  In  some  skulls  this  tubercle  is  long 
enough  to  unite  with  the  apex  of  the  anterior  clinoid  process,  so  that  the 
artery,  in  emerging  from  the  groove,  passes  through  a  ring  of  bone.  The 
two  '  clinoid '  processes  on  each  side  give  attachment  to  the  '  tentorium 
cerebelli.'  The  pituitary  fossa  is  bounded  behind  by  a  square  plate  of  bone, 
which,  as  it  represents  the  back  of  the  saddle,  is  termed  the  '  dorsum 
sellae.'  The  corners  of  this  plate  project  and  form  what  are  called  the 
'  posterior  clinoid  processes,' — thus  named  from  their  fancied  resemblance 
to  bed-posts.  These  are  directly  opposite  to  the  *  anterior  clinoid  pro- 
cesses,' of  which  we  shall  speak  presently.  The  posterior  surface  of  the 
plate  slopes  very  obliquely  backward,  is  continuous  with  the  basilar  pro- 
cess of  the  occipital  bone,  and  forms  an  inclined  plane  which  supports 
the  '  pons  Varolii. '  Lastly,  in  the  side  of  the  plate  there  is  generally  a 
notch  which  transmits  the  sixth  nerve. 

The  posterior  surface  of  the  body  is  connected  with  the  basilar  process 
of  the  occipital  bone,  in  young  subjects  by  cartilage,  in  adults  by  bone, 
so  that  after  a  certain  age  it  is  impossible  to  separate  the  '  basilar  suture ' 
without  the  saw.  The  section  shows  well  the  structure  of  this  part  of  the 

85  This  name  was  given  to  it  by  Galen,  who  thought  that  it  secreted  the  '  pituita, ' 
or  mucus,  and  that  this  passed  down  into  the  throat  through  the  small  foramina 
which  are  often  found  at  the  bottom  of  the  fossa  ('  De  usu  partium,'  lib.  ix.cap.  1). 
Its  functions  are  not  even  yet  understood;  it  is  generally  classed  as  a  '  ductless'  or 
'  vascular  gland, '  along  with  the  spleen  and  thyroid  body. 


58  HUMAN    OSTEOLOGY. 

base  of  the  skull;  namely,  two  plates  of  compact  bone  separated  by  about 
•^  of  an  inch  of  cancellous  tissue  or  '  diploe.'  Thus  the  bone  is  light 
and  shocks  transmitted  to  the  base  of  the  skull  are  broken.  (Plate  XI. 
Fig.  1.) 

Cornua  Sphenoidalia. — The  anterior  surface  of  the  body  (Plate 
X.  Fig.  2)  fits  the  posterior  part  of  the  ethmoid  bone.  It  presents  in 
the  middle  line  a  perpendicular  plate  of  bone  termed  the  'rostrum/ 
This  forms  part  of  the  bony  septum  of  the  nose,  and  is  connected  in  front 
with  the  perpendicular  plate  of  the  ethmoid  bone,  and  below  with  the 
vomer;  as  may  be  seen  in  Plate  XXIII.  Fig.  1.  The  surface  of  bone  on 
each  side  of  the  rostrum  is  completed  by  two  plates  of  bone,  one  on  each 
side,  termed  the  'cornua  sphenoidalia'  or  'sphenoidal  turbinated  bones.' 
Although  apparently  integral  parts  of  the  sphenoid,  yet  these  little  bones 
are  formed  each  from  a  special  centre  of  ossification,  are  distinct  in  early 


FIG.  14.— Cornua  Sphenoi  FIG.  15. 

life,  and  remain  separable  till  adult  age.  The  annexed  drawing  (Fig. 
14)  shows  the  *  cornua  sphenoidalia '  removed  in  a  perfect  state.  The  ros- 
trum of  the  sphenoid  would  fit  into  the  gap  between  them.  Each  cornu 
is  triangular  with  the  apex  downward.  Each  completely  walls  in  the 
sphenoidal  cell  of  its  own  side,  except  at  the  upper  part,  where  there  is  a 
round  opening  in  the  base  of  the  cornu  which  admits  air  from  the  upper 
meatus  of  the  nose.  Fig.  15  represents  one  of  the  cornua  seen  from  the 
surface  toward  the  sphenoidal  cell.  It  shows  the  thin  scales  of  bone 
which  project  into  the  cell  and  assist  in  lining  its  walls.  However,  it  is 
right  to  state  that  these  cornua  sphenoidalia  are  rarely  met  with  perfect. 
In  consequence  of  their  coalescence  with  the  sphenoid,  ethmoid,  and 
palate  bones,  they  are  generally  broken  in  the  process  of  separation,  so  that 
there  appears  in  most  sphenoid  bones  a  large  irregular  hole  leading  into 
the  cell;  as  shown  on  one  side  of  Plate  X.  Fig.  2. 

Sphenoidal  Cells. — Next  come  the  'sphenoidal  cells'  or  sinuses. 
These  are  large  air  cavities  in  the  body  of  the  sphenoid,  generally  two  in 
number,  and  separated  by  a  more  or  less  complete  perpendicular  parti- 


SPHENOID     BONE.  59 

tion.  (Plate  XXIII.  Figs.  1  and  2.)  Like  the  other  air-cells  in  the  bones 
of  the  skull,  they  are  not  developed  in  young  subjects;  but  in  the  adult 
they  gradually  become  large  enough  to  excavate  the  whole  body  of  the 
bone.  The  air  is  admitted  freely  into  them  from  the  upper  meatus  of 
the  nose  through  an  opening  in  the  front  wall  of  each  sinus;  and  they  are 
lined  with  a  prolongation  from  the  nasal  mucous  membrane.  This 
communication  of  the  sphenoidal  cells  with  the  nasal  cavities  explains 
how  bleeding  from  the  nose  may  occur  as  a  symptom  of  fracture  through 
the  base  of  the  skull, — that  is,  through  the  body  of  the  sphenoid. 

Lastly,  the  sides  of  the  anterior  surface  of  the  body  are  hollowed  out 
into  two  or  three  small  air-cells,  one  below  the  other.  (Plate  X.  Fig.  2.) 
Of  these,  the  upper,  one  or  more,  are  roofed  in  by  corresponding  cells  of 
the  ethmoid  bone;  and  the  lower  by  a  corresponding  cell  in  the  orbital 
process  of  the  palate  bone. 

The  inferior  surface  of  the  body  (Plate  XI.  Fig.  1)  assists  in  forming 
the  roof  of  the  nasal  fossae;  and  the  posterior  part  of  this  surface,  con- 
tinuous with  the  basilar  process  of  the  occipital  bone,  looks  toward  the 
upper  part  of  the  throat,  and  may  therefore  be  called  the  '  guttural '  sur- 
face. A  portion  of  the  vertical  plate  or  '  rostrum '  is  seen  here  also.  Ob- 
serve that  it  is  expanded  a  little  toward  its  base.  Now  it  is  this  lower 
part  of  the  rostrum  which  is  connected  with  the  vomer,  and  the  mode  of 
connection  is  rather  singular.  The  rostrum  fits  into  a  deep  cleft  be- 
tween the  two  plates  or  '  wings '  of  the  vomer,  and  thus  serves  as  a  foun- 
dation from  which  this  bone  passes  forward  and  forms  the  septum  of  the 
nose.  But  the  chief  thing  to  notice  on  this  surface  is  a  process  or  scale 
of  bone  which  projects  horizontally  inward,  on  each  side,  from  the  base 
of  the  internal  pterygoid  plate.  These  are  termed  the  '  vaginal  processes,' 
and  their  free  edges  rise  just  enough  to  allow  the  edges  of  the  vomer  to 
slide  beneath  them.  This  is  another  contrivance  which  fixes  the  vomer. 
Lastly,  each  of  these  plates  is  traversed  by  a  small  groove,  or  perhaps  a 
complete  canal,  termed  the  '  ptery go-palatine  canal,'  which  transmits  the 
pterygo-palatine  artery,  and  a  posterior  branch  (the  pharyngeal  nerve) 
from  the  spheno-palatine  ganglion.  The  artery  is  a  branch  of  the  inter- 
nal maxillary,  runs  from  before  backward,  and  supplies  the  top  of  the 
pharynx  and  the  Eustachian  tube. 

So  much  for  the  anterior,  posterior,  superior,  and  inferior  surfaces  of 
the  body  of  the  sphenoid.  All  that  we  have  to  remark  concerning  the  sides 
of  the  body  is,  that  they  are  grooved  for  the  carotid  artery,  and  that  the 


60  HUMAN    OSTEOLOGY. 

smooth  plate  of  the  body  in  front  of  the  sphenoidal  fissure  contributes  to 
form  a  part  of  the  inner  wall  of  the  orbit.  (Plate  XXII.) 

Lesser  Wings. — The  lesser  wings  (or  orbito-sphenoids)  project  trans- 
versely from  the  upper  part  of  each  side  of  the  body.  (Plate  X.  Pig.  1.) 
Their  upper  surface  is  smooth  and  flat,  and  supports  the  anterior  lobes 
of  the  brain;  their  lower  surface  overhangs  the  sphenoidal  fissure,  and 
forms  the  back  part  of  the  roof  of  the  orbit:  hence  they  are  sometimes 
called  the  '  orbital  wings.'  Their  anterior  margins  are  serrated  and  articu- 
late with  the  orbital  plates  of  the  frontal  bone;  their  posterior  margins 
are  free,  and  in  life  fit  into  the  great  fissure  (of  Sylvius)  between  the  an- 
terior and  middle  lobes  of  the  cerebrum.  Their  base  is  traversed  by  the 
'  foramen  opticum,'  through  which  pass  the  optic  nerve  and  ophthalmic 
artery  into  the  orbit.  This  foramen  should  be  described  rather  as  a  short 
canal  directed  outward  and  forward.  Toward  the  '  sella  Turcica '  each 
wing  projects  considerably  in  the  form  of  a  blunt  angle,  termed  the  '  ante- 
rior clinoid  process ';  and  between  this  and  the  body  of  the  sphenoid  there 
is  either  a  deep  notch  or  a  complete  ring  for  the  internal  carotid  artery. 

Greater  Wings. —  The  '  greater  wings/  sometimes  called  the  '  tem- 
poral '  (or  alisphenoids),  project  from  the  lower  part  of  each  side  of  the 
body.  Each  wing  presents  three  surfaces,  which  respectively  enter  into 
the  formation  of  the  base  of  the  cranium,  the  orbit,  and  the  temple.  The 
'cerebral  surface'  is  concave,  and  marked  by  the  convolutions  of  the 
middle  lobe  of  the  brain.  The  'orbital  surface'  is  a  smooth  quadrilateral 
plate  which  forms  more  than  half  of  the  outer  wall  of  the  orbit.  (Plate 
XVI.  Fig.  2.)  Of  the  four  borders  of  this  plate,  notice  that  the  superior 
articulates  with  the  frontal  bone,  and  the  anterior  with  the  malar  bone  ; 
while  the  posterior  enters  into  the  formation  of  the  '  sphenoidal  fissure ' 
and  the  inferior  into  the  '  sphenomaxillary '  fissure.  The  'temporal 
surface '  is  divided  into  two  unequal  parts  by  a  transverse  '  crest '  of  bone; 
of  these,  the  upper  and  larger  one  forms  part  of  the  temporal  fossa,  and 
gives  origin  to  part  of  the  temporal  muscle:  the  lower  one,  which  is  more 
horizontal,  forms  part  of  the  zygomatic  fossa,  and  gives  origin  to  one 
head  of  the  '  pterygoideus  externus.'  The  posterior  angle  of  the  great 
wing  terminates  in  a  sharp  process  termed  the  '  spinous  process,'  which  fits 
into  the  angle  between  the  squamous  and  petrous  portions  of  the  temporal 
bone,  and  gives  attachment  to  the  internal  lateral  ligament  of  the  lower 
jaw,  as  well  as  origin  to  the  '  laxator  tympani '  muscle. 

Sphenoidal  Fissure. — The  greater  wings  are  separated  from  the 


SPHENOID     BONE.  61 

lesser  by  a  broad  and  long  fissure,  termed  the  '  sphenoidal  fissure/  which 
leads  from  the  cranial  cavity  into  the  orbit,  and  transmits  nerves  to  the 
eye  and  its  appendages.  The  sphenoidal  fissure  gives  passage  to  the  third 
and  fourth  nerves,  to  the  first  or  ophthalmic  branch  of  the  fifth,  the  sixth, 
a  few  filaments  of  the  sympathetic  nerve,  and  also  to  the  ophthalmic 
vein.  Immediately  below  the  inner  end  of  this  fissure  is  the  *  foramen 
rotundum/  which  transmits  the  superior  maxillary  division  of  the  fifth 
nerve.  Farther  back  and  more  external  is  the  '  foramen  ovale/  which 
transmits  the  inferior  maxillary  division  of  the  fifth  nerve,  the  lesser  pe- 
trosal  nerve,  and.  the  small  meningeal  branch  of  the  internal  maxillary 
artery.  Near  the  spinous  process  is  the  '  foramen  spinosum/  through 
which  the  '  arteria  meningea  media '  enters  the  skull.  Besides  the  foramina 
in  the  greater  wing,  there  is  often  one  (near  the  outer  edge  of  the  sphe- 
noidal fissure)  which  leads  into  the  orbit,  and  transmits  a  branch  of  the 
middle  meningeal  artery.  There  is  often  another  between  the  foramen 
spinosum  and  the  foramen  ovale,  through  which  a  small  vein  passes;  this 
is  termed  the  '  foramen  Vesalii/ 

Pterygoid  Processes. — The  'pterygoid  processes'  descend  nearly 
perpendicularly  from  the  under  part  of  the  bone, — one  on  either  side, 
and  act  as  buttresses  which  support  the  upper  jaw  bones.  Each  process 
consists  of  two  parts  termed  the  '  internal '  and  '  external  pterygoid '  plates. 
These  are  united  in  front,  but  diverge  from  one  another  behind,  forming 
a  deep  interval  called  the  '  pterygoid  fossa/  At  its  lower  part  the  '  ptery- 
goid fossa '  presents  a  deep  notch  which  in  the  complete  skull  is  filled  up 
by  the  tuberosity  of  the  palate  bone.  The  external  plate  is  broader  than 
the  internal  and  gives  origin  to  the  '  pterygoideus  externus'  and  the 
'  pterygoideus  internus '  muscles  on  its  external  and  internal  surfaces  re- 
spectively. These  muscles  cause  the  grinding  movement  in  mastication. 
Its  outer  surface  also  forms  the  floor  of  the  zygomatic  fossa.  Respecting 
the  internal  pterygoid  plate,  observe  that  it  forms  the  lateral  and  part  of 
the  superior  boundary  of  the  posterior  opening  of  the  nose,  and  that  it  has 
a  crescent-shaped  margin  above,  leaving  room  for  the  cartilage  of  the  Eu- 
stachian  tube.  At  the  root  of  this  plate  is  a  shallow  groove  called  the 
'  scaphoid  fossa '  which  gives  origin  to  the  '  tensor  palati '  muscle,  the  ten- 
don of  which  plays  round  a  notch  on  the  '  hamular '  process  at  the  end  of 
the  internal  pterygoid  plate.  Behind  the  last  molar  tooth  of  the  upper 
jaw  we  can  distinctly  feel  this  hamular  process.  Lastly,  through  the  base 
of  the  internal  pterygoid  plate,  a  long  canal,  the  '  pterygoid '  or  '  Vidian/ 


62  HUMAN    OSTEOLOGY. 

runs  from  before  backward,  and  transmits  the  '  Vidian'  '•  ('  great  petrosal ') 
nerve  and  artery. 

Look  now  at  the  anterior  aspect  of  the  pterygoid  process,  and  observe 
a  plate  of  bone,  standing  off  like  a  side  buttress  which  connects  it  with  the 
greater  wing.  The  plane  of  this  plate  forms  a  smooth  surface,  termed 
the  '  spheno-maxillary,'  and  nearly  corresponds  in  direction  with  that  of 
the  'orbital  surface'  of  the  greater  wing.  (Plate  X.  Fig.  2.)  We  draw 
special  attention  to  this  plate,  and  give  it  the  special  name  of  spheno- 
maxillary  surface  because  it  constitutes  the  posterior  wall  of  a  deep  fossa, 
termed  the  'spheno-maxillary,'  which,  in  the  perfect  skull,  intervenes 
between  the  sphenoid  and  superior  maxillary  bones. 

Connections. — The  sphenoid  is  connected  with  twelve  bones,  includ- 
ing all  those  of  the  cranium  and  five  of  the  face.  The  '  body '  is  connected 
behind  with  the  occipital  bone  by  the  basilar  suture;  in  front  with  the 
ethmoid  bone,  the  two  palate  bones,  and  the  vomer.  The  '  lesser  wing ' 
is  connected  to  the  orbital  plate  of  the  frontal  bone:  the  'greater  wing' 
is  connected  to  the  orbital  plate  of  the  frontal  by  a  rugged  surface  of  con- 
siderable extent,  to  the  anterior  inferior  angle  of  the  parietal  bone,  to 
the  squamous  and  petrous  parts  of  the  temporal  bone;  and  to  the  malar 
bone.  Lastly,  the  pterygoid  processes  are  connected  with  the  palate 
bones.97 

Ossification. — In  the  early  foatus  the  sphenoid  bone  consists  of  several 
parts.  The  posterior  part  of  the  body,  termed  by  scientific  anatomists, 
the  '  basisphenoid '  or  *  post-sphenoid,'  is  ossified  from  two  centres,  placed 
side  by  side  in  the  sella  Turcica.  Later  on  another  pair  of  centres  (one 
on  each  side  of  the  former)  appear,  making  in  all  four  for  the  basisphenoid 
part. 

The  greater  wings,  termed  '  alisphenoids,'  have  each  a  distinct  centre, 
from  which  the  external  pterygoid  plates  are  also  ossified. 

The  front  part  of  the  body,  termed  '  presphenoid,'  has  two  centres;  its 
lesser  wings  (orbito-sphenoids)  each  have  one  ossific  nucleus. 

Lastly,  the  internal  pterygoid  plates  and  the  sphenoidal  turbinated 
bones  have  each  their  separate  nucleus  of  ossification.  The  bone  then  as 
a  whole  has  fourteen  centres. 

36  Vidus  Vidius  was  a  professor  at  Paris,  and  physician  to  Fra^ois  I. 

37  In  some  skulls,  in  which  the  malar  bone  does  not  enter  into  the  composition  of 
the  spheno-maxillary  fissure,  the  sphenoid  meets  the  superior  maxillary  bone.     In 
such  exceptional  skulls  the  sphenoid  would  be  connected  with  seven  bones  of  the 
face. 


SPHENOID     BONE.  63 

As  the  preceding  description  may  appear  a  little  confusing  to  a  be- 
ginner, the  following  plan  will  explain  it  better,  and  at  the  same  time  re- 
fresh the  memory  on  the  chief  elements  of  the  entire  bone." 

PLAN  OF  THE  OSSIFIC  CENTRES  OF  THE  SPHENOID  BONE. 

CORNU  SPHENOIDALE  CORNU  SPHENOIDALE 

(Sphenoidal  turbinated).  (Sphenoidal  turbinated). 

LESSEE  WING  FRONT  OF  BODY  LESSER  WING 

(Orbito- sphenoid).  (Presphenoid).  (Orbito-sphenoid). 

I  11  1 

BACK  OF  BODY. 

(Basisphenoid) . 

GREATER  WING         2  2         GREATER  WING 

(Alisphenoid)  (Alisphenoid) 

and  external  pterygoid  plate.  and  external  pterygoid  plate. 

1  '  1 

INTERNAL  PTERYGOID  PLATE      INTERNAL  PTERYGOID  PLATE 

(Pterygoid).  (Pterygoid). 

1  1 

Comparative  Osteology. — The  top  of  the  great  wing  of  the  sphe- 
noid, passing  up  between  the  frontal  and  temporal  bones,  articulates  with 
the  anterior  inferior  angle  of  the  parietal  bone.  The  union  of  these  two 
bones  separates  the  temporal  from  the  frontal.  In  those  types  of  men 
where  the  forehead  slopes  backward,  these  bones  approximate,  and  in 
some  cases  actually  articulate  with  each  other.  (Nor.  Hum.  Ost.,  Nos. 
1159,  1160,  1161,  and  1146.)  The  size  and  strength  of  the  external 
pterygoid  plate  bear  a  direct  relation  to  the  development  of  the  pterygoid 
muscles  which  cause  the  grinding  movements  of  mastication;  conse- 
quently, it  is  highly  developed  in  ruminants  (see  skulls  of  the  deer  and  ox). 

In  old  skulls  the  sphenoidal  cells  often  extend  into  part  of  the  basilar 
process  of  the  occipital  bone.  In  the  chimpanzee  the  sphenoidal  cells 
extend  far  into  the  alisphenoid  and  pterygoid  bones. 

38  The  cornua  sphenoidalia  begin  to  ossify  about  the  time  of  birth,  and  do  not 
unite  to  the  body  of  the  bone  till  the  age  of  puberty.  The  internal  pterygoid  plates 
are  developed  from  membrane,  and  begin  to  ossify  about  the  fourth  month.  For  full 
information  on  the  development  of  the  sphenoid  bone,  see  Meckel's  '  Archiv,'  B.  1, 
and  Quain's  '  Anatomy,'  8th  edition. 


64  HUMAN    OSTEOLOGY. 

THE  ETHMOID    BONE. 
(PLATE  XI.  FIGS.  2  and  8.) 

Constituent  Parts. — This  remarkably  light  and  spongy  bone  con- 
tains the  organ  of  smell.  It  occupies  the  interval  between  the  orbital 
plates  of  the  frontal  bone,  and  enters  into  the  formation  of  the  cranium, 
the  orbit,  and  the  nose.  It  appears,  at  first  sight,  complicated;  but  it 
is  simple  when  one  understands  the  plan  of  it.  It  consists  of  a  horizontal 
plate,  which  forms  part  of  the  base  of  the  skull;  of  a  central  perpendicu- 
lar plate  which  forms  part  of  the  septum  of  the  nose;  and  of  two  '  lateral 
masses '  containing  the  air-cells.  Each  of  these  must  be  examined  sepa- 
rately. 

Cribriform  Plate. — The  horizontal  plate  fits  into  the  '  notch '  be- 
tween the  orbital  plates  of  the  frontal  bone;  and  completes  the  anterior 
fossa  of  the  base  of  the  skull.  (Plate  XIX.)  It  is  called  the  'cribriform 
plate '  (cribrum,  T^UOS-,  a  sieve),  because  it  is  perforated  by  holes  for  the 
passage  of  the  olfactory  nerves.  High  above  it  rises  a  crest  of  bone, 
termed,  from  its  resemblance  to  a  cock's  comb,  the  '  crista  galli.'  This, 
which  is  a  continuation  of  the  perpendicular  plate,  gradually  rises  from 
behind,  swells  out  as  it  proceeds,  and  stopping  suddenly  short,  presents  a 
broken  edge  which  is  connected  to  the  frontal  bone. 

The  '  crista  galli '  serves  for  the  attachment  of  the  '  falx  cerebri.'  It 
varies  in  size,  and  has  often  a  slight  lateral  inclination.  Sometimes  it 
contains  an  air-cell.  The  cribriform  plate  does  not  come  up  to  the  level 
of  the  lateral  masses,  but  lies  at  the  bottom  of  a  deep  groove  ('  olfactory 
groove'),  which,  being  divided  by  the  crista  galli  in  the  middle,  forms  in 
the  perfect  skull  two  recesses  which  lodge  and  support  the  olfactory  lobes 
of  the  bmin.  The  foramina  at  the  bottom  are  arranged  on  each  side  in 
three  somewhat  irregular  rows, — an  outer,  an  inner,  and  a  middle.  Pass 
bristles  down  these  holes,  and  you  will  find  that  the  inner  and  the  outer 
rows  lead  respectively  to  the  '  olfactory  canals '  on  the  perpendicular 
plate  and  the  upper  spongy  bones;  while  the  middle  holes  run  simply 
through  the  cribriform  plate.  These  three  rows  of  holes  correspond  to 
the  three  sets  of  olfactory  nerves:  namely,  those  that  ramify  on  the  sep- 
tum, those  that  ramify  on  the  spongy  bones,  and  those  that  supply  the 
roof  of  the  nose.  (Plate  XXIII.  Figs.  1  and  2.)  Close  to  the  front  of 


PLATE  XI. 


Vidian  canal. 


Scaphoid 
fossa •'''* 

?tery£oid  fossa 


I   1 


'Vagi  nal  process$A£ 
Pterygo  palatine  canaL 


"Sup1?  constrictor 
cp  Pharynx. 


Perpendicular  plate.. 


AntTEthmoidal  cells  <;''' 


r  Ethrno,dal  ceV,tf-<" 


InfundibuYum. 


Crista^adli. 

..Slit  for  theNasa] Nerve. 
..Ant^ethrr.oidal  foramen . 


CTibriForfn  plate . 
ETHMOIDBONE 


Ul Middle  Spongy  bone. 


Perpendicular  tal  ate . 


THE    ETHMOID    BONE.  65 

the  '  crista  galli '  is  a  long  '  slit/  rather  than  a  hole,  which  gives  passage 
to  the  *  nasal  nerve '  (a  branch  of  the  first  division  of  the  fifth  pair),  which 
confers  common  sensation  upon  the  mucous  membrane  as  well  as  the  skin 
of  the  nose. 

Perpendicular  Plate. — The  perpendicular  plate  descends  from  the 
cribriform  plate  and  assists  in  forming  the  septum  of  the  nose.  Notice 
the  numerous  grooves  and  canals  on  its  surface,  for  the  passage  of  the 
olfactory  nerves.  Its  connections  are  well  shown  in  Plate  XXIII.  Fig.  1. 
Behind,  it  is  connected  along  a  sloping  line  with  the  '  rostrum '  of  the 
sphenoid  and  the  vomer:  in  front,  it  is  connected  with  the  nasal  spine 
of  the  frontal  and  the  crest  of  the  two  nasal  bones,  of  which  it  mainly 
supports  the  arch.  The  triangular  gap  in  the  septum  in  the  dry  skull  is 
filled  up,  in  the  recent  state,  by  the  central  cartilage  of  the  nose. 

Lateral  Masses. — The  '  lateral  masses '  of  the  ethmoid  (Fig.  16)  are 
made  up  of  irregular  air-cells,  surrounded  by  paper-like  walls  of  bone, 
lined  by  mucous  membrane  con- 
tinuous with  that  of  the  nose. 
The  cells  are  divided  into  two  sets, 
— an  anterior  and  a  posterior;  and 
the  cells  of  one  set  do  not  commu- 
nicate with  those  of  the  other. 
In  the  separated  bone  many  of  the 
cells  are  necessarily  opened,  be- 
cause their  walls,  in  the  perfect 
skull,  are  completed  by  the  adjoin- 
ing bones.  Thus,  the  front  cells  r 

Fia.  16.— Transverse  Section,  to  show  the  Lateral 

on   the  upper  surface  are  roofed  Air  Ceils  of  the  Ethmoid  Bone, 

in  by  corresponding  cells  in  the  orbital  plate  of  the  frontal;  those  at 
the  back  of  the  bone  are  closed  by  the  body  of  the  sphenoid  and  the 
orbital  process  of  the  palate  bone;  those  in  front  of  the  bone  are  walled 
in  by  the  lachrymal;  those  below,  by  the  superior  maxillary  bone.  On 
the  outer  side  of  each  lateral  mass  the  cells  are  closed  by  a  smooth  and 
square  plate  of  bone,  termed  the  'os  planum/  belonging  entirely  to  the 
ethmoid.  This  forms  a  large  share  of  the  inner  wall  of  the  orbit  (Plate 
XXII.),  where  it  is  easy  to  learn  its  connections  with  the  surrounding 
bones,  by  tracing  the  sutures  between  them.  Lastly,  notice  the  two 
notches  on  its  upper  border,  which,  with  the  frontal,  form  the  '  anterior 

and  posterior  ethmoidal  foramina/    The  '  anterior  '  transmits  the  nasal 
5 


66  HlTMAtf   OSTEOLOGY. 

nerve  and  the  anterior  ethmoidal  vessels;  the  '  posterior '  gives  passage 
to  the  posterior  ethmoidal  vessels. 

Turbinated  Bones  and  Meatus.— On  the  inner  aspect  of  the  lat- 
eral mass  we  observe  two  thin  plates  of  bone  standing  out,  one  below  the 
other,  and  slightly  curled,  like  a  turbinated  shell.  These  are  the  '  tur- 
biirated'  or  'spongy'  bones  of  the  ethmoid  (Plate  XI.  Fig.  3),  and  can  be 
properly  seen  only  in  a  divided  skull.  The  '  superior '  is  the  smaller  of 
the  two,  and  does  not  reach  so  far  forward  as  the  other,  which  is  called 
the  '  middle/  because  there  is  a  third  or  '  inferior  turbinated '  bone,  still 
lower  down  in  the  nose;  but  this  does  not  belong  to  the  ethmoid.  Now 
the  spaces  left  between  these  turbinated  bones  and  the  lateral  masses  are 
called  respectively  the  superior  and  middle  '  meatus,'  or  passages  of  the 
nose.  Each  is  distinct  from  the  other,  and  leads  to  its  own  particular 
cavities,  and  to  no  other.  The  superior  meatus,  being  farther  back  than 
the  middle,  leads  into  the  sphenoidal  cell,  and  into  the  posterior  eth- 
moidal cells.  The  middle  meatus  leads  into  the  anterior  ethmoidal  cells, 
and  also  to  the  frontal  cells,  along  a  funnel-shaped  canal  ('  infundibu- 
lum ')  which  traverses  the  foremost  of  the  ethmoidal.  (Plate  XXIII. 
Fig.  2.) 

Unciform  Process. — Lastly,  from  the  anterior  part  of  each  lateral 
mass  an  irregular  plate  of  bone  descends  almost  perpendicularly,  and 
terminates  in  a  kind  of  hook;  hence  it  is  called  the  '  unciform39  process ' 
(Plate  XL  Fig.  3).  By  referring  to  Plate  XXIII.  Fig.  2,  it  is  seen  that 
this  process  is  connected  with  the  inferior  spongy  bone,  and  with  the  thin 
walls  of  the  '  antrum*  of  the  superior  maxillary  bone;  it  chiefly  assists  in 
narrowing  the  orifice  of  this  great  air-cavity. 

Connections. — The  ethmoid  is  connected  with  thirteen  bones, 
namely, — behind,  with  the  sphenoid  and  two  palate  bones;  above,  with  the 
frontal;  below,  with  the  two  superior  maxillary;  in  front,  with  the  two 
lachrymal  bones.  The  perpendicular  plate  is  connected  behind  with  the 
vomer,  and  in  front  with  the  two  nasal  bones.  Lastly,  the  unciform  pro- 
cess on  each  side  is  connected  with  the  inferior  spongy  bone  and  the 
superior  maxillary. 

Ossification. — Until  the  middle  of  foetal  life  the  ethmoid  is  all  carti- 
lage. Ossification  begins  about  the  fifth  month,  by  a  centre  for  each 
of  the  lateral  parts,  and  gradually  extends  into  the  two  upper  turbinated 

39  The  '  unciform  process'  is  almost  always  broken  in  taking  the  skull  to  pieces; 
but  it  is  evident  enough  in  a  good  section  of  the  nasal  cavities. 


THE   ETHMOID   BONE.  67 

bones  (ethmo-turbinals).  Within  a  year  after  birth  another  centre  ap- 
pears for  the  perpendicular  and  cribriform  plates  (mesethmoid).  An 
arrest  in  the  progressive  ossification  of  the  perpendicular  plate  occasions  a 
'pug  nose/  In  the  foetus  at  birth  there  are  no  ethmoid  cells;  these  are 
not  formed  until  the  fourth  or  fifth  year. 

Comparative  Osteology. — In  man  the  rule  is  that  there  are  three 
turbinated  bones  on  each  side;  sometimes  there  is  a  fourth,  smaller  than 
the  rest,  and  higher  up  at  the  back  part.  This  fourth  bone  is  more  fre- 
quently met  with  in  some  colored  races  where  the  sense  of  smell  is  notori- 
ously acute. 

The  curled  plates  of  the  turbinated  bones  are  covered  by  a  very  vas- 
cular membrane.  The  upper  ones  afford  an  extensive  surface  upon 
which  the  olfactory  nerves  are  distributed  after  their  passage  through  the 
cribriform  plate.  By  the  variation  of  the  extent  of  surface  of  these  bones 
it  will  be  seen  that  the  acuteness  of  the  sense  of  smell  and  the  capability 
of  warming  the  air  on  its  way  through  the  nose  to  the  lungs  are  regulated. 

The  sense  of  smell  is  remarkably  keen  in  the  deer  tribe  and  carnivora, 
and  their  spongy  bones  are  developed  in  proportion.  It  is  curious  that 
they  should  both  in  a  measure  depend  for  a  living  upon  the  development 
of  the  same  sense,  the  one  to  avoid  its  enemies,  and  the  other  to  find  its 
prey. 

The  spongy  bones  on  which  the  nerves  of.  smell  are  distributed  and 
those  which  are  only  covered  by  a  vascular  membrane,  are  widely  differ- 
entiated in  their  conformation  in  the  lower  animals.  In  the  seal,  for  in- 
stance (Nos.  3934,  3935A),  which  inhabits  the  arctic  regions  and  neces- 
sarily breathes  intensely  cold  air,  the  inferior  spongy  bones  subdivide 
into  a  multitude  of  plates  and  afford  a  vast  surface  on  which  is  distrib- 
uted a  profusion  of  blood-vessels  which  warm  the  air  before  entering 
the  lungs.  The  surface  of  these  bones  has  been  estimated  at  about  120 
square  inches  in  each  nostril;  a  longitudinal  section  of  such  a  nostril  has 
the  appearance  of  being  completely  plugged  by  the  convoluted  warming 
plates  of  the  lower  spongy  bone;  while  those  on  which  the  olfactory 
nerves  are  distributed  have  a  different  form  and  are  further  back  and 
separated  by  a  slight  interval  from  the  others. 

There  is  no  ethmoid  bone  in  serpents,  but  the  olfactory  filaments  are 
spread  out  on  a  plicated  mucous  membrane. 


BONES  OF  THE  FACE. 

THEKE  are  fourteen  bones  of  the  face;  namely,  the  two  superior  max*. 
illary,  the  two  malar,  the  two  nasal,  the  two  lachrymal,  the  two  inferior 
spongy,  the  two  palate,  the  vomer,  and  the  inferior  maxilla. 


SUPEEIOK  MAXILLAEY  BONE. 
(PLATE  XII.) 

Constituent  Parts. — This  bone  gives  much  character  to  the  human 
face,  and  forms  the  greater  part  of  its  framework.  It  is  exceedingly 
irregular  in  shape,  and,  besides  forming  sockets  for  the  teeth,  enters  into 
the  composition  of  the  nose,  the  orbit,  the  cheek,  and  the  palate.  For 
convenience  of  description,  we  divide  it  into  a  l  body/  which  is  hollowed 
out  into  a  large  air-cavity,  called  the  'antrum/  and  four  outstanding 
'  processes';  namely,  the  '  alveolar/  which  holds  the  teeth;  the  '  palatine/ 
which  forms  part  of  the  hard  palate;  the  '  nasal/  which  assists  in  form- 
ing the  nose;  and  the  'malar/  which  helps  to  form  the  prominence  of  the 
cheek. 

Body:  Walls  of  Antrum.— Let  us  take  the  '  body '  first,  and  learn 
its  various  relations  well,  for  it  is  a  part  of  great  surgical  interest,  being 
liable  to  many  diseases  requiring  surgical  operations.  The  first  thing  to 
observe  is,  that  the  walls  which  bound  its  cavity  have  four  aspects:  one 
— namely,  the  front — looks  toward  the  cheek;  another,  the  upper,  looks 
toward  the  orbit;  a  third,  the  inner,  looks  toward  the  nose;  and  a 
fourth,  behind,  looks  toward  the  zygomatic  fossa.  Therefore,  when  a 
morbid  growth  forms  in  the  antrum,  and  distends  it,  any  one  or  more  of 
these  walls  may  be  protruded.  They  are  all  very  thin,  the  orbital  espe- 
cially; but  it  is  worth  remembering  that  they  are  thicker  in  the  child 
than  in  the  adult. 

Antrum:  Anterior  Wall. — The  anterior  wall  of  the  '  antrum '  is  that 


SUPERIOR  MAJCfLLARY  BONE. 


TuToer-os-ity ,^  "r1"~ 


Lachrymal  groove   VgflS  ;\ Nasal  process. 

iTTf'ocu-H,  °gA_TeTldo^cwli. 


Fig.l. 


Infra-orlaita.1  foramen. 


i — Depressor alae  nsi&i. 


Myrtiform  fosst 


Canine  fossa.. 


Sur»fa.ce. 


AntCnisal  spine 
Pa'lkte  pUtc 


Inner   Surface. 


SUPERIOR    MAXILLARY   BONE.  69 

which  is  generally  removed  to  take  out  a  morbid  growth  from  the  inte- 
rior, and  through  which  we  tap  the  antrum  to  let  out  pus,  or  any  fluid 
that  may  have  accumulated  there;  cysts  in  the  antrum  being  by  no  means 
uncommon.  There  is  a  depression  in  it,  called  the  '  canine  fossa,'  a  little 
outside  the  eminence  of  the  canine  tooth;  and  above  this  is  the  '  infra- 
orbital  foramen/  or  termination  of  the  '  infra-orbital  canal/  which  trans- 
mits the  '  infra-orbital '  nerve  and  artery.  The  canine  fossa  gives  origin 
to  the  'levator  anguli  orts.'  Above  the  infra-orbital  foramen  arises  the 
'levator  labii  superioris,'  and  more  internally  the  'compressor  naris.' 

Antrum:  Posterior  Wall. — The  posterior  wall  of  the  antrum  is 
convex,  and  bulges  into  the  zygomatic  fossa.40  There  are  several  small 
holes  in  it,  leading  to  canals  ('dental  canals')  which  transmit  the  pos- 
terior dental  branches  of  the  superior  maxillary  nerve,  and  the  superior 
dental  branches  of  the  internal  maxillary  artery.  Lower  down  it  has 
a  very  rough  surface,  just  behind  the  wisdom  tooth,  called  the  '  tuber- 
osity/  by  which  it  is  firmly  connected  to  the  palate  bone;  and  along  the 
inner  edge  of  this  surface  (Plate  XII.  Fig.  2)  is  a  groove,  which,  with  the 
perpendicular  plate  of  the  palate  bone,  forms  the  '  posterior  palatine 
canal/  for  the  passage  of  the  descending  palatine  nerve  and  artery. 

Antrum:  Superior  Wall. — The  superior  wall  of  the  antrum  slopes 
downward  and  outward,  and  forms  the  floor  of  the  orbit.  Like  the  other 
walls  of  the  antrum,  it  is  thin  enough  to  be  translucent.  Notice  here  the 
'  infra-orbital  canal/  for  the  passage  of  the  superior  maxillary  nerve  and 
infra-orbital  artery.  It  commences  behind  as  a  groove,  but  soon  becomes 
a  canal,  which  terminates  on  the  front  wall  of  the  antrum,  just  below 
the  edge  of  the  orbit.  A  little  before  its  termination,  the  main  canal 
gives  off  one  or  sometimes  two  smaller  ones,  not  always  visible,  termed 
the  '  anterior  dental  canals.'  These  run  down  in  the  very  substance  of 
the  front  wall  of  the  antrum,  and  transmit  blood-vessels  and  nerves  to 
the  two  incisor,  the  canine,  and  the  first  bicuspid  teeth.  To  see  these 
canals  it  is  necessary  to  introduce  a  bristle  as  a  guide,  and  then  to  rasp  away 
the  front  wall  of  the  bone.  Near  the  lachrymal  groove  may  sometimes  be 
seen  a  small  depression,  indicating  the  spot  where  the  '  inferior  oblique ' 
muscle  of  the  eye  arises.  This  is  the  only  muscle  of  the  orbit  which  takes 
origin  from  the  front;  all  the  others  arise  from  the  back  part,  around  the 

40  Blandin  ('  Anat.  Topog. '  p.  44)  relates  a  case  in  which  a  tumor,  originating  in 
the  antrum,  made  its  way  into  the  zygomatic  fossa,  and  caused  a  swelling  in  the 
{emple. 


70  HUMAN    OSTEOLOGY. 

optic  foramen.  In  the  perfect  skull  (Plate  XVI.)  observe  that  the  upper 
wall  or  '  orbital  plate '  of  the  antrum  is  connected  on  its  inner  side  with 
the  lachrymal,  ethmoid,  and  palate  bones;  but  that  on  its  outer  side  it 
forms  one  of  the  margins  of  the  '  spheno-maxillary  fissure/  at  the  back  of 
the  orbit. 

Antrum:  Internal  Wall. — On  the  inner  or  '  nasal  wall '  of  the  an- 
trum, the  first  thing  to  notice  is  the  orifice  of  the  antrum  itself.  (Plate 
XII.  Fig.  2.)  In  the  separate  bone,  this  orifice  is  very  irregular,  and 
large  enough  to  admit  the  end  of  a  finger;41  but  in  the  perfect  skull 
(Plate  XXII.)  it  is  very  much  closed  in  by  thin  plates  from  the  ethmoid, 
the  palate,  and  the  inferior  spongy  bones.  In  the  recent  state  the  orifice 
is  generally  so  contracted  by  a  fold  of  the  mucous  membrane  of  the  nose, 
that  it  will  only  admit  a  crow-quill.  The  orifice  is  not  near  the  bottom 
of  the  antrum,  but  very  high  up:  the  consequence  of  this  is,  that  when 
fluid  collects  in  the  antrum  it  cannot  run  out  until  the  antrum  is  nearly 
full,  or  until  the  head  is  inclined  horizontally  with  the  opposite  cheek 
downward. 

Antrum,  Cavity  of. — The  '  maxillary  sinus/  or  ' antrum/43  is  by  far 
the  largest  of  the  air-cells  in  the  bones  of  the  head.  It  is  lined  by  mucous1 
membrane  continuous  with  that  of  the  nose,  and  is  large  enough  to  hold 
a  musket-ball  with  ease.  A  ball  has  been  known  to  lodge  in  the  antrum 
for  months,  and  even  for  years,  before  it  was  removed.43  A  ball  once 
lodged  for  eleven  years  in  the  antrum,  and  finally  made  its  way  out 
through  the  roof  of  the  mouth.44  However,  it  varies  in  size,  and  some- 
what in  shape,  in  different  persons;  but,  as  a  rule,  it  has  the  form  of  a  tri- 
angular pyramid,  with  the  base  toward  the  nose,  and  the  apex  toward  the 
malar  bone.  Thin  plates  of  bone  often  project  into  the  antrum,  making 
a  kind  of  recess  or  pocket  here  and  there; 45  and  the  fangs  of  one  or  more 
of  the  molar  teeth  generally  project  into  it,  either  quite  bare,  or  covered 
by  a  thin  scale  of  bone.  Hence  the  practice,  adopted  by  some  surgeons, 
of  drawing  one  of  these  teeth,  say  the  first  or  second  molar,  to  let  out 
matter  from  the  antrum.  Again,  the  fangs  of  decayed  or  otherwise  in- 

41  Sometimes  there  are  two  openings,  separated  by  the  thin  plate  (unciform  pro- 
cess) which  descends  from  the  ethmoid  bone. 

42  Nathaniel  Highmore  was  an  English  anatomist,   born  1613,  died  1684,  who 
wrote  much  about  the  diseases  of  the  antrum.    He  did  not  discover  the  antrum,  for 
it  was  known  to  Galen  as  the  '  sinus  maxillaris. ' 

43  '  Commentaries,'  p.  528.     Guthrie. 

44  '  Anatomic  Chirurgicale. '    Mr.  Jarjavay. 

45  See  a  curious  case  by  Catlin,  '  Trans.  Odontolog.  Soc.'  vol.  ii.  1857. 


•SUPERIOR   MAXILLARY   BONE.  71 

jured  molar  teeth  are  liable  to  set  up  disease  in  the  antrum;  and  this  is 
the  explanation  commonly  given  why  morbid  growths  arise  in  the  antrum 
more  frequently  than  in  any  other  of  the  air-cavities  of  the  nose. 

The  following  case  gives  a  good  idea  of  the  extent  of  the  antrum:  — 
'  A  lady  suffering  from  tooth-ache  submitted  to  the  extraction  of  the  ca- 
nine tooth  of  the  upper  jaw,  with  which  a  portion  of  the  alveolar  process 
was  removed,  making  an  aperture  in  the  antrum,  from  which  a  watery 
fluid  constantly  issued.  The  patient,  desirous  of  ascertaining  the  source 
of  the  discharge,  took  a  pen,  and  having  stripped  off  the  barbs  from  the 
feathered  part,  found  that  the  whole  of  it,  full  six  inches  long,  could  be 
introduced  into  the  cavity.  At  this  she  was  greatly  terrified,  believing 
it  must  have  gone  into  the  brain.  She  consulted  Highmore,  who  ex- 
plained to  her  that  the  pen  had  turned  spirally  within  the  sinus,  and  he, 
besides,  counselled  her  to  submit  with  patience  to  the  inconvenience  of 
the  discharge  from  the  cavity.'4' 

Alveolar  Process  and  Teeth.  —  The  alveolar  process  is  a  thick  and 
strong  ridge  of  bone,  curved  so  as  to  form  with  that  of  the  other  side  the 
dental  arch.  It  consists  of  two  plates,  an  outer  and  an  inner,  connected 
by  numerous  septa  which  form  the  sockets  (alveoli)  of  the  teeth.  The 
inner  plate  is  the  stronger;  therefore,  in  drawing  a  tooth,  care  should  be 
taken  to  incline  it  a  little  outward.  The  outer  plate  is  marked  by  emi- 
nences corresponding  to  the  fangs  of  the  teeth;  the  eminence  of  the  canine 
tooth  being  especially  marked. 

In  a  child,  from  the  end  of  the  second  to  the  end  of  the  sixth  year,  the 
half  of  each  jaw  contains  sockets  for  five  teeth,  i.e.  for  two  incisors,  one 
canine,  and  two  molars. 

The  formula  for  the  '  milk  dentition  '  is  therefore  — 


The  half  of  each  jaw  contains,  in  the  adult,  sockets  for  eight  teeth; 
namely,  two  '  incisors/  one  '  canine/  two  '  bicuspids  (or  prae-molars)  '  and 
three  '  molars.'  Thus  the  dental  formula  of  the  adult  human  skull  is  — 

.2+2        1+1         2+2    w3+3_33i      n 
~*'2+2'    *I+T   ^2+2'  W'3+3~' 

The  eruption  of  the  second  or  permanent  set  of  teeth  commences  about 
45  Drake's  '  System  of  Anatomy,'  8vo.  1707. 


72  HUMAN    OSTEOLOGY. 

the  end  of  the  sixth  year.  The  first  to  appear  is  the  first  permanent 
molar,  which  is  therefore  called  the  six-year-old  tooth,  and  is  the  oldest 
tooth  in  an  adult's  head.  The  presence  of  this  tooth  has  been  used  as  a 
test  of  age  by  medical  inspectors  in  giving  certificates  as  to  the  fitness  of 
children  to  work  in  factories.47 

Generally  speaking,  the  twenty  milk  teeth  are  cut  between  the  6th 
and  24th  months,  and  the  thirty -two  permanent  teeth  between  the  6th  and 
24th  years.48 

Sockets  of  Teeth. — The  sockets  correspond  in  number  and  size  to 
the  fangs  of  the  teeth  they  receive.  They  vary  in  depth  in  different  in- 
stances. The  deepest  of  all  is  the  socket  of  the  canine  tooth:  this  is  often 
-fo  of  an  inch  in  depth  in  the  dry  bone.  The  first  two  molars  of  the 
upper  jaw  have  three  fangs  each,  and  as  many  sockets.  Of  these  fangs, 
two  are  external,  one  internal.  In  the  last  molar,  or  wisdom  tooth,  the 
fangs  are  generally  consolidated  into  one.  Irregularities  in  the  shape  and 
the  direction  of  the  fangs,  whether  diverging  too  much  or  converging, 
lead  to  unavoidable  evils  when  it  is  necessary  to  extract  them.  Either  a 
fang  breaks,  or  part  of  the  alveolus  must  be  extracted  with  the  fang.  One 
cannot  foresee  this.  Hence  it  follows  that,  now  and  then,  even  the  most 
skilful  operators  break  teeth  or  extract  portions  of  bone.  At  the  bottom 
of  each  socket  is  a  minute  hole,  through  which  the  vessels  and  nerve  come 
up  and  supply  the  pulp  cavity;  and  there  are  also  numerous  holes  in  the 
bony  partitions  between  the  sockets,  through  which  vessels  supply  the 
gums  and  the  periosteum.  These  are  the  sources  of  the  bleeding  after 
the  extraction  of  a  tooth.  The  teeth  are  fixed,  not  only  by  the 
closely  fitting  socket,  but  also  by  the  very  vascular  membrane,  the  perios- 
teum, which  lines  the  socket  and  adheres  closely  to  the  fang.  This  peri- 
osteum not  only  retains  the  teeth  in  their  places,  but  helps  to  maintain 
their  vitality,  and,  being  elastic,  breaks  shocks  which  would  otherwise  be 
communicated  to  the  jaws.  When  the  dental  periosteum  inflames,  the 
tooth  is  partly  lifted  out  of  its  socket,  and  the  teeth  cannot  be  clenched 
without  pain.  If  the  inflammation  goes  on  to  the  formation  of  matter, 
the  periosteum  quits  its  hold  of  more  or  less  of  the  fang,  and  abscess  in 
the  socket  is  the  result.  The  matter  then  makes  its  way  out  by  the  side 
of  the  tooth,  or  through  a  small  hole  formed  by  ulceration  in  the  alveolar 
wall;  that  is,  a  gumboil  is  the  result.  In  the  dry  bones,  most  of  the  teeth 

47  ' The  Teeth  a  test  of  Age,'  in  a  pamphlet  by  Edwin  Saunders,  1837. 

48  'Dental  Anatomy,'  p.  179.     Tomes,  1876. 


SUPERIOR   MAXILLARY   BONE.  73 

fall  out,  because  the  periosteum  shrinks,  and  thus  the  sockets  become  too 
large. 

The  alveolar  process  gives  origin  to  two  muscles  (Plate  XII.  Fig.  1), 
namely,  to  the  '  buccinator '  above  the  three  molar  teeth,  and  to  the  '  de- 
pressor alae  nasi '  above  the  incisor  teeth,  where  there  is  a  little  depression, 
termed  the  'myrtiform  fossa/ 

Nasal  Process. — The  nasal  process  ascends  nearly  perpendicularly, 
in  a  line  with  the  canine  tooth,  and  abuts,  by  means  of  a  very  rough 
suture,  upon  the  internal  angular  process  of  the  frontal  bone.  It  supports 
the  true  nasal  bones,  and  contributes  to  form  the  inner  margin  of  the 
orbit.  The  principal  point  concerning  the  nasal  process  is  the  deep  groove 
which  runs  almost  vertically  behind  its  orbital  margin.  It  is  called  the 
'  lachrymal  groove.'  In  the  perfect  skull  it  is  converted  into  a  complete 
canal  by  a  corresponding  groove  in  the  lachrymal  bone  and  a  small  por- 
tion of  the  inferior  spongy  bone.  The  canal  thus  completed  lodges  the 
'  lachrymal  sac '  and  '  nasal  duct/  which  convey  the  tears  into  the  inferior 
'  meatus '  of  the  nose.  It  is  about  the  size  of  a  common  goose-quill. 
When,  from  inflammation  or  other  cause — such  as  a  tumor — the  canal 
becomes  obstructed,  the  tears  necessarily  flow  over  and  run  down  the 
cheek.  To  obviate  this,  it  is  often  requisite  to  slit  up  one  of  the  lachry- 
mal canaliculi,  and  introduce  a  probe  into  the  nasal  duct.  Therefore  one 
must  know  well  the  direction  of  the  lachrymal  canal.  It  runs  from  above 
downward,  and  slightly  backward.  On  the  outer  surface  of  the  nasal 
process  is  the  prominent  ridge  which  forms  the  inner  margin  of  the  orbit. 
This  gives  origin  to  the  '  tendo  oculi '  or  '  palpebrarum '  and  the  '  orbicu- 
laris  oculi.'  A  little  in  front  of  this  the  'levator  labii  superioris  et  alae 
nasi '  arises.  On  the  inner  surface  are  the  two  ridges  to  which  the  inferior 
and  middle  spongy  bones  are  attached,  and  also  the  smooth  surfaces  be- 
tween the  ridges  which  respectively  form  part  of  the  inferior  and  middle 
'  meatus '  of  the  nose.  Near  the  top  the  nasal  process  often  closes  in  one 
of  the  anterior  ethmoidal  cells  at  the  lower  half.  In  front  the  nasal  pro- 
cess presents  a  sharp  crescent-shaped  margin,  which,  with  the  similar  one 
on  the  opposite  bone  and  the  nasal  bones,  bounds  the  anterior  opening  of 
the  nose,  and  gives  attachment  to  the  lateral  cartilage. 

Palatine  Process. — The  palatine  process  extends  horizontally  in- 
ward, and  forms  the  anterior  two-thirds  of  the  hard  palate,  and  the  floor 
of  the  nose;  the  posterior  third  being  completed  by  the  palate  bone.  It 
is  slightly  arched  from  before  backward,  and  is  thicker  in  front,  near  the 


74  HUMAN   OSTEOLOGY. 

alveolus,  than  behind.  On  the  palatine  surface  (Plate  XX.)  can  be  seen 
— 1,  the  palatine  groove  for  the  descending  palatine  vessels  and  nerve;  2, 
the  numerous  foramina  which  transmit  vessels  into  the  bone;  and  3,  the 
pits  made  by  the  palatine  glands.  The  upper  or  nasal  surface  is  smooth 
and  slightly  concave.  By  adjusting  the  two  superior  maxillary  bones  to- 
gether, you  find  that  the  palatine  processes  are  connected  in  the  middle 
line  by  a  very  rough  suture  (palatine  suture) ;  and  that  they  rise  toward 
the  nose  in  a  crest,  which  articulates  with  the  vomer,  and  forms  the 
base  of  the  bony  septum  of  the  nose.  (Plate  XXIII.  Fig.  1.)  This  crest 
projects  in  front  in  the  shape  of  a  sharp  spine  (the  '  anterior  nasal  spine'), 
to  which  is  attached  the  cartilaginous  part  of  the  septum.  In  this  pala- 
tine suture,  immediately  behind  the  middle  incisor  teeth,  we  see  the  '  ante- 
rior palatine  canal/  (Plate  XX.)  Toward  the  palate  this  canal  has,  at 
first  sight,  only  one  large  orifice;  but  if  we  look  to  the  bottom  of  it,  we 
shall  probably  find  four  minute  openings.  Two  of  these 49  lie  in  the  mid- 
dle line,  one  behind  the  other,  and  transmit  the  naso-palatine  nerves; 
the  other  two  much  larger,  are  situated  one  on  each  side  of  the  middle 
line;  they  lead  into  the  floor  of  each  nostril,  and  transmit  the  anterior 
palatine  arteries.50 

Malar  Process. — The  malar  process  stands  off  from  the  outer  side 
of  the  antrum.  It  is  remarkably  thick  and  strong,  and  is  connected,  by 
a  very  rugged  triangular  surface,  with  the  malar  bone.  The  malar  pro- 
cess is  situated  just  over  the  first  and  second  molar  teeth,  and  is  there- 
fore well  calculated  to  resist  pressure  in  mastication.  When  we  crack  a 
nut,  we  instinctively  place  it  under  these  teeth. 

Connections. — The  superior  maxilla  is  connected  with  nine  bones, 
as  follows: — With  the  malar,  the  frontal,  the  nasal,  the  lachrymal,  the 
vomer,  the  inferior  spongy,  the  palate  bone,  its  fellow,  and  lastly,  the 
ethmoid.  We  mention  this  bone  last  of  all,  because  we  wish  to  direct 
attention  to  a  fact  which  we  have  hitherto  omitted  to  notice,  that  some 
of  its  cells  are  closed  in  by  half  cells  usually  seen  along  the  orbital  plate 
of  the  superior  maxillary  bone.  (Plate  XII.  Fig.  2.) 

49  These  '  incisor'  foramina  are  sometimes  called  the  foramina  of  '  Scarpa. ' 

50  These  lateral  foramina  are  sometimes  called  the  foramina  of  'Stenson.'    The 
description  in  the  text  concerning  the  anterior  palatine  canals  applies  to  twenty  out 
of  forty  skulls  examined.     Their  disposition,  in  other  cases,  is  very  apt  to  vary,  both 
as  to  number  and  size.    It  was  Scarpa  ('Annot.  Anatom. '  lib.  ii.  p. 75)  who  first  pointed 
out  the  varieties  in  these  canals.     In  many  instances  one  of  the  canals  is  absent;  or, 
if  present,  not  pervious  throughout.    For  a  more  complete  explanation  of  this  ques- 
tion, see  Quain's  'Anatomy.' 


SUPERIOR   MAXILLARY   BONE.  75 

Ossification. — The  ossification  of  the  upper  jaw  begins  about  the 
seventh  week  of  foetal  life,  and  proceeds  so  quickly,  that  the  number  of  its 
independent  centres  has  not  yet  been  accurately  determined.  It  appears 
to  have  five  distinct  centres:  one  for  the  alveolus  behind  the  incisors,  one 
for  the  palatine  process,  one  for  the  floor  of  the  orbit  and  malar  process, 
a  fourth  for  the  portion  in  front  of  the  antrum  with  the  nasal  process, 
and  lastly,  a  very  distinct  centre,"  which  includes  the  sockets  of  the  two 
incisor  teeth.  In  most  human  skulls,  if  not  very  old,  one  can  trace  the 
remains  of  the  'pre-maxillary'  suture.  (Plate  XX.)  It  runs  outward 
from  the  anterior  palatine  canal,  and  then  through  the  alveolar  border  of 
the  jaw,  invariably  between  the  second  incisor  and  the  canine  tooth;  and 
here  we  lose  all  trace  of  it.  This  is  interesting  surgically.  In  cases  of 
double  hare-lip,  where  the  fissure  is  not  confined  to  the  lips,  the  pre- max- 
illary bones  on  each  side  fail  to  unite  with  the  rest  of  the  upper  jaw,  and 
often  project  in  a  hideous  manner  through  the  fissure  of  the  lip.  When 
removed  by  operation,  these  bones  are  always  found  to  contain  the  cap- 
sules of  the  four  incisor  teeth." 

Right  or  Left  ? — This  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body,  if  he  hold  the  nasal  process  (which 
articulates  with  the  frontal)  upward,  the  opening  of  the  antrum  inward, 
and  the  incisor  teeth  forward. 

Comparative  Osteology. — The  teeth  which  grow  from  the  pre- 
maxillary  bones  are  called  incisors.  On  a  close  inspection  of  the  narwhal 
hanging  in  the  Mus.  Roy.  Coll.  Surg.  the  sharp  spiral  tusk  will  be  found 
to  spring  from  the  left  pre-maxillary  bone.  It  is  therefore  the  left  in- 
cisor tooth.  The  right  one  usually  remains  undeveloped;  but  there  is  a 
specimen  in  the  Cambridge  Museum  where  both  are  of  full  length.  Evi- 
dence of  the  narwhal's  power  of  offence  or  defence  is  given  by  the  tusks 
having  been  found  buried  to  a  depth  of  ten  or  twelve  inches  in  the  tim- 
bers of  ships.  The  female  narwhal  has  no  such  extraordinary  growth 
of  the  incisor  tooth.  It  is  interesting  to  notice  in  the  skull  of  the  ele- 
phant that  the  suture  between  the  superior  maxillary  and  pre-maxillary 
bones  is  visible,  and  that  his  tusks  grow  from  the  pre-maxillary  bones,  and 
are  therefore  also  incisor  teeth.  The  tusks  of  the  walrus  have  their  origin 

61  This  part,  in  man,  was  first  pointed  out  by  the  poet  Goethe. 

62  For    the  most  recent   investigations  concerning   the  'Formation  and  Early 
Growth  of  the  Bones  of  the  Human  Face, '  see  a  very  interesting  and  elaborate  paper 
by  Mr.  G.  W.  Callender  in  the  'Philosoph.  Trans.'  for  1869. 


76  HUMAN   OSTEOLOGY. 

externally  to  the  pre-maxillary  bone,  and  are  therefore  canine  teeth,  and 
this  animal  belongs  to  the  carnivora.  (No.  3864A.) 

Examine  the  bull,  and  it  will  be  seen  that  there  are  no  incisors  in  the 
upper  jaw.  This  is  the  case  in  all  the  Kuminants,  excepting  the  camel, 
which  loses  the  central  incisors  early  in  life.  In  the  bull,  deer,  and  other 
Euminants  also  notice  that  the  so-called  canines  in  the  lower  jaw  are  in 
a  regular  series  with  the  six  incisors,  and  much  resemble  them.  They 
seize  their  food  between  this  even  row  of  teeth  and  the  prehensile  upper 
lip,  and  then  chew  it  with  the  molars. 

In  the  order  Monotremata,  the  one  member,  Echidna,  has  no  teeth, 
and  the  other,  Ornithorhynchus  paradoxus,  has  but  horny  plates  to  repre- 
sent them.  (See  Sep.  Ser.) 

In  many  of  the  lower  animals  teeth  are  not  confined  to  the  alveolar 
margins  of  the  jaw,  but  are  found  scattered  about  the  upper  part  of  the 
alimentary  canal.  Thus,  in  the  Labroid  fishes  (No.  96),  large  teeth  may 
be  seen  developed  upon  the  palate.  In  the  perch  there  are  teeth  in  the 
pharynx.  (No.  197.)  In  the  lobster  there  are  horny  teeth  in  the  stomach, 
•where  the  food  is  ground. 

In  birds  the  superior  maxillary,  with  the  inter-maxillary  bones,  are 
prolonged  forward,  and  when  covered  with  the  appropriate  horny 
material,  constitute  the  beak;  the  lower  jaw  also  projecting  forms  the 
lower  half  of  the  beak.  (Nos.  1678,  1678A.) 

The  upper  jaw  is  movable  in  parrots  (No.  1438),  and  has  a  broad  trans- 
verse articulation  with  the  frontal.  It  consists  of  the  coalesced  nasal, 
maxillary,  and  pre-maxillary  bones. 

In  Primates  there  are  never  more  than  four  incisors  above,  and  the 
same  number  below. 

In  the  Eodents  the  incisors  continue  to  grow  throughout  life,  and  are 
long  and  curved.  See  the  Canadian  beaver  (No.  2165). 

In  Cetacea  the  pre-maxillae,  which  are  small  in  proportion  to  the  max- 
illae, are  prolonged  far  in  advance  of  the  nasal  aperture,  as  may  be  seen 
in  the  skeleton  of  the  great  sperm  whale  in  the  Mus.  Eoy.  Coll.  Surg. 

Examine  the  poison  fang  in  a  serpent  from  New  Holland  (No.  650). 
It  is  situated  in  the  upper  jaw  and  has  a  bristle  passed  through  it,  show- 
ing that  it  is  tubular.  This  tube  contains  the  duct  of  the  poison  gland. 

Look  at  the  plates  of  whalebone  hanging  from  the  upper  jaw  of  the 
whalebone  whale.  It  is  by  means  of  these  plates  that  he  entangles  the 
small  molluscs  on  which  he  feeds. 


PLATE  XIII. 


Sphenoid  sur  face  _^®\     'JX,-EtWioid  surface. 

^r.ijc-*^^' 
"Ridoefbi  midU'.e  spongy  bonev 


INTERNAL  VIEW  OF   PALATE     BONE. 


Anterior  or  Ma.xilla.ry  surface 


!Exbrn»1 


Internal  orEthmoida.1 


l'osterio'r  or.,  SpTienoiol  surfajce  . 
of  the  orb'ta.1  process  of  the  Palate  bone. 


Malar  canals 


Orbital  curface  . 


articulalcs  «* 
infenor  Spongy  bona.. 


LACHRYMAL  BONE. 


MALAR   BONE. 


MALAR   BONE.  77 

MALAK    BONE. 
(PLATE  XIII.  Fig.  3.) 

Three  Surfaces. — The  malar  bone  forms  the  prominence  of  the 
cheek,  a  part  of  the  margin  and  wall  of  the  orbit,  and  the  greater  portion 
of  the  zygomatic  arch.  It  is  remarkably  thick  and  strong,  and  resists 
injury,  to  which  the  face,  in  this  situation,  is  so  exposed.  We  divide  it 
into  an  anterior  or  subcutaneous  surface,  a  superior  or  orbital,  and  a  poste- 
rior or  zygomatic. 

On  the  subcutaneous  surface  there  is  nothing  to  observe  except  the 
orifice  of  one  of  the  '  malar  canals/  and  that  it  gives  origin  to  the  '  zygo- 
maticus  major '  and  '  minor '  muscles. 

The  superior  surface  forms  part  of  the  outer  wall  of  the  orbit,  a  small 
part  of  its  floor,  and,  generally  speaking,  the  corner  only  of  the  spheno- 
maxillary  fissure. "  There  are  usually  two  '  malar  canals '  to  be  seen  on 
it.  By  introducing  bristles,  it  will  be  found  that  one  of  these  leads  to 
the  subcutaneous  surface;  the  other,  to  the  zygomatic  surface.  These 
malar  canals  transmit  cutaneous  nerves  which  proceed  from  the  orbital 
branch  of  the  superior  maxillary  nerve  to  the  cheek,  and  the  zygomatic 
fossa  respectively. 

The  posterior  surface  is  very  concave,  and  forms  the  anterior  wall  of 
the  zygomatic  fossa. 

Three  Borders. — The  malar  bone  has  three  free  borders.  One 
forms  at  least  a  third  of  the  margin  of  the  orbit,  and  reaches  as  far  in- 
ward as  the  infra-orbital  canal,  giving  origin  to  a  few  fibres  of  the  '  leva- 
tor  labii  superioris';  a  second  forms  the  upper  edge  of  the  zygomatic 
arch,  and  running  upward  becomes  continuous  with  the  temporal  ridge 
at  the  external  angular  process  of  the  frontal  bone — this  border  gives 
attachment  to  the  '  temporal  fascia ';  a  third  forms  the  lower  edge  of  the 
arch,  and  gives  origin  to  the  '  masseter '  muscle.  (Plate  XV.  Fig.  2.) 

Connections. — The  malar  bone  is  connected  with  four  bones:  namely, 
by  a  broad  and  very  roughly  serrated  surface,  with  the  superior  maxillary; 

53  From  an  examination  of  many  skulls,  I  find  that  the  malar  bone  is  excluded 
from  the  spheno-maxillary  fissure  more  frequently  than  is  generally  supposed.  This 
exclusion  is  effected  in  one  of  two  ways;  either  by  the  immediate  junction  of  the 
superior  maxillary  and  sphenoid  bones,  or  by  the  interposition  of  a  little  '  Wormian' 
bone  just  at  the  angle  of  the  fissure. 


78  HUMAN    OSTEOLOGY. 

"by  suture,  with  the  external  angle  of  the  frontal,  the  orbital  plate  of  the 
sphenoid,  and  the  zygomatic  process  of  the  temporal.  These  several  con- 
nections are  so  strong  that  the  bone  cannot  be  driven  inward  toward  the 
orbit,  and  fractures  of  it  are  very  rare. 

Ossification. — It  is  developed  from  a  single  centre  of  ossification, 
which  appears  about  the  seventh  week  of  foetal  life. 

Right  or  Left  ? — The  cheek  bone  will  be  in  the  same  position  as  the 
corresponding  one  in  the  student's  body  if  he  hold  it  with  the  subcuta- 
neous surface  forward  (and  outward);  the  orbital  surface  upward;  and 
the  articulation  for  the  zygoma  backward. 

Comparative  Osteology. — The  upper  process  of  the  malar  bone 
does  not  articulate  with  the  frontal  in  the  carnivora  (Nos.  4561,  4562). 

In  the  Great  Kangaroo  and  Wombat  the  zygomatic  process  of  the 
malar  bone  extends  backward  so  far  that  it  forms  part  of  the  glenoid 
cavity  and  articulates  with  the  lower  jaw. 


NASAL  BONE. 
(PLATE  XVI.  Fig.  3.) 

The  nasal  bones,  situated  one  on  either  side,  occupy  the  space  between 
the  nasal  processes  of  the  superior  maxillary  bones,  and,  together,  com- 
plete the  bridge  of  the  nose.  Their  length,  breadth,  and  degree  of  in- 
clination, determine  the  shape  of  the  nose.  We  have  to  examine  their 
anterior  and  posterior  surfaces,  and  their  four  borders. 

Surfaces. — Their  anterior  surfaces  are  subcutaneous,  convex,  and 
present  the  orifices  of  one  or  more  canals,  which  transmit  blood-vessels. 

Their  posterior  surfaces  are  concave,  form  part  of  the  roof  of  the  nose, 
and  each  is  marked  by  a  groove  for  the  passage  of  the  external  branch  of 
the  nasal  division  of  the  fifth  nerve. 

Borders. — Their  upper  borders  are  broad,  serrated,  and  firmly  articu- 
lated with  the  frontal  bone.  Their  lower  borders  are  thin  and  free  in  the 
dry  bone,  but  connected  in  the  recent  subject  with  the  lateral  cartilages  of 
the  nose.  Each  has,  generally,  a  little  notch  in  it,  through  which  the  ex- 
ternal branch  of  the  nasal  nerve  comes  and  supplies  the  skin  at  the  tip  of 
the  nose.  Their  outer  borders  are  serrated,  slightly  sloped,  and  rest 


NASAL    BONE.  79 

upon  the  nasal  processes  of  the  superior  maxillary  bones.  Their  inner 
borders  articulate  with  each  other,  in  the  middle  line,  along  the  '  nasal 
suture.*  From  the  under  surface  of  this  suture  a  high  '  crest'  of  bone 
projects.  By  putting  the  bones  together,  it  is  seen  how  their  crests  form 
the  beginning  of  the  bony  septum  of  the  nose,  and  how  they  articulate 
with  the  nasal  spine  of  the  frontal  bone,  and  the  perpendicular  plate  of 
the  ethmoid.  (Plate  XXIII.  Fig.  1.)  Hence,  with  a  depressed  fracture 
of  the  nasal  bones,  there  must  be  a  fracture  of  the  perpendicular  plate  of 
the  ethmoid.  In  some  rare  instances,  the  injury  extends  through  the 
perpendicular  plate  of  the  ethmoid  to  the  base  of  the  brain.  Observing 
the  great  strength  of  the  nasal  bones  and  the  massive  arch  they  form, 
how  the  sides  of  this  arch  are  supported  by  the  nasal  processes  of  the  su- 
perior maxillae,  while  the  centre  is  propped  up  by  the  nasal  spine  of  the 
frontal  bone,  and  the  perpendicular  plate  of  the  ethmoid  (Plate  XXIV. 
Fig.  2),  one  can  readily  understand  what  makes  the  arch  so  strong,  and 
why  the  bones  are  so  seldom  broken.  A  pretty  good  proof  is  given  of  the 
strength  of  the  arch,  when  one  sees  a  mountebank  support  upon  it,  with 
impunity,  a  ladder,  with  the  additional  weight  of  a  man  upon  the  steps. 

Connections. — The  nasal  bone  articulates  with  four  others,  namely, 
its  fellow,  the  superior  maxillary,  the  frontal,  and  the  perpendicular  plate 
of  the  ethmoid. 

Ossification. — Each  nasal  bone  is  developed  from  a  single  centre  of 
ossification,  which  appears  about  the  seventh  week  of  foatal  life. 

Right  or  Left? — This  bone  will  be  in  the  same  position  as  the  corre- 
sponding one  in  the  student's  body  if  he  hold  the  thick  border  (which 
articulates  with  the  frontal  bone)  upward,  the  convex  surface  forward  and 
outward,  and  the  short  side  (for  articulation  with  its  fellow)  inward. 

Comparative  Osteology. — The  only  difference  between  the  skulls 
of  a  tiger  and  a  lion  is  that  in  the  lion  the  upper  ends  of  the  nasal  bones 
and  the  nasal  processes  of  the  superior  maxillary  bones  are  on  the  same 
level,  whereas  in  the  tiger  the  nasal  bones  run  up  considerably  beyond 
the  nasal  processes. 


80  HUMAN    OSTEOLOGY. 

LACHRYMAL  BONE. 

(PLATE  XIII.    Fig.   4.) 

Surfaces. — The  lachrymal  bones  are  situated,  one  on  each  side,  on 
the  inner  wall  of  the  orbit.  They  are  exceedingly  thin  and  delicate,  and 
shaped  somewhat  like  a  finger-nail;  hence  the  name  'os  unguis.'  In  old 
skulls,  they  are  often  as  thin  as  silver  paper,  and  sometimes  perforated. 
One  surface  is  directed  toward  the  orbit;  the  other  toward  the  nose.  One 
of  these  bones  is  seen  in  siM  in  Plate  XVI.  Fig.  2. 

The  external  or  orbital  surface  has  a  vertical  ridge  upon  it  which  ter- 
minates below  in  a  small  hook-like  process  or  tongue,  termed  '  hamulus,' 
which  fits  into  the  angle  between  the  inferior  turbinated  and  the  superior 
maxillary  bones  (Plate  XXIII.  Fig.  2).  In  front  of  this  is  a  groove 
('lachrymal  groove'),  which,  together  with  the  groove  on  the  nasal  pro- 
cess of  the  superior  maxilla,  forms  the  commencement  of  the  canal  for 
the  passage  of  the  tears  from  the  lachrymal  sac  into  the  nose.  The  ridge 
itself  gives  origin  to  the  'tensor  tarsi.'  The  bone  behind  the  ridge  is 
smooth,  slightly  concave,  and  forms  part  of  the  inner  wall  of  the  orbit. 

The  internal  or  nasal  surface  presents  a  slight  furrow  corresponding 
to  the  external  ridge.  The  surface  in  front  of  this  forms  part  of  the 
middle  meatus  of  the  nose;  that  behind  it  always  covers  the  anterior  cells 
of  the  ethmoid  bone,  and  sometimes  a  small  cell  or  two  in  the  frontal 
bone. 

Connections. — By  examining  the  orbit  (Plate  XVI.  Fig.  2),  you  ob- 
serve that  the  lachrymal  bone  is  somewhat  square,  and  that  it  articulates 
by  suture  with  the  frontal  above,  the  ethmoid  behind,  the  superior  maxil- 
lary in  front  and  below.  But  this  is  not  all.  The  hook-like  process 
(hanmlus)  at  the  lower  edge  of  the  bone  articulates  with  what  is  called 
the  'lachrymal  process'  of  the  inferior  turbinated  bone.  (Plate  XXIII. 
Fig.  2.)  So,  then,  it  articulates  with  four  bones. 

Ossification. — It  has  one  centre  of  ossification,  which  appears  about 
the  eighth  week  of  foetal  life. 

Right  or  Left? — This  bone  will  be  in  the  same  .position  as  the  corre- 
sponding one  in  the  student's  body,  if  he  hold  the  concave  orbital  surface 
outward,  the  lachrymal  groove  forward,  and  the  small  tongue-like  process 
(which  articulates  with  the  lachrymal  process  of  the  inferior  turbinated 
bone)  downward. 


PLATE  XIV. 


Orbital  surFa.ce. 

Zybornatic  surface 

$-pVieno-palat'rne  foramen 


..SpVienoiolal  surface. 


lit 


Posterior  palatine   canal j;|  A  ...."Rid^efbr  inferior  spongy \>one. 

M 


Tuberosiby 

Groove  co'mpletirig  ptery^oicl  fbssa 


iior'i7.o  n  tal  plate  - 


Rst 


PALATE  BONE. 


OnFi'ce  of  posterior  p»Uti'ne  canaL 


for  T<  'Accessory  palatine  canals. 

.r  surPace. 


EtVimoidal  surface 


urface  of 
oiclal  process 


ian  crest 


OrWiba.\  surface 
ll a.ry  surface. 


... Tuber 


Anterior  view 


PALATE    BONE.  81 

PALATE  BONE. 
(PLATES  XIII.  and  XIV.) 

Each  '  palate  bone '  is  wedged  in  between  the  pterygoid  process  of  the 
sphenoid  and  the  superior  maxillary  bone.  Each  forms  part  of  the  nasal 
fossa,  of  the  orbit,  and  of  the  palate.  As  the  palate  bone  somewhat  re- 
sembles the  letter  L  in  shape,  we  can  divide  it,  for  convenience  of  descrip- 
tion, into  a  horizontal  and  a  vertical  plate. 

Horizontal  Plate. — The  horizontal  plate  completes  the  bony  palate 
by  fitting  on  to  the  palate  plate  of  the  superior  maxillary  bone.  Its  under 
surface  (Plate  XIV.  Fig.  2)  presents  a  transverse  ridge  for  the  insertion 
of  the  aponeurosis  of  the  '  tensor  palati.'  In  front  of  this  ridge  and  to- 
ward its  outer  end  we  observe  the  orifice,  more  or  less  complete,  of  the 
'  posterior  palatine  canal,'  for  the  transmission  of  the  descending  palatine- 
vessels  and  the  larger  palatine  nerve  from  the  spheno-palatine  ganglion, 
The  anterior  edge  of  this  plate  is  serrated  and  cut  obliquely,  so  as  to 
articulate  with,  and  be  supported  by,  the  palate  plate  of  the  superior 
maxilla.  The  posterior  edge  is  smooth  and  concave,  and  gives  attachment 
to  the  soft  palate.  The  inner  edge  firmly  articulates  with  its  fellow,  by 
means  of  a  '  median  crest '  raised  up  toward  the  nose,  precisely  like  the 
corresponding  parts  in  the  superior  maxillary  bones  (see  Plate  XXIII. 
Fig.  1):  this  crest  supports  the  vomer,  and  forms  a  basis  for  the  septum 
of  the  nose.  Behind  it  terminates  in  a  pointed  process,  termed  the 
'posterior  nasal  spine'  (Plate  XX.),  which  gives  origin  to  the  'azygos 
uvulae '  muscle.  The  upper  surface  of  the  plate  is  smooth  and  slightly 
concave,  thus  forming  part  of  the  floor  of  the  nose. 

Vertical  Plate. — The  vertical  plate  of  the  palate  bone  contributes  to 
form  the  outer  boundary  of  the  nasal  fossa.  On  its  inner  surface  (Plate 
XIII.  Fig.  1)  is  a  '  ridge '  to  which  is  attached  the  inferior  turbinated 
bone.  The  surfaces  above  and  below  this  ridge,  respectively,  form  part 
of  the  middle  and  inferior  '  meatus '  of  the  nose.  Still  higher  is  a  ridge 
for  the  middle  turbinated  bone.  On  its  outer  surface  we  observe  a  rertical 
groove,  which  either  alone,  or  in  conjunction  with  the  superior  maxilla, 
forms  the  '  posterior  palatine  canal/  which  transmits  the  descending 
palatine  vessels  and  the  large  palatine  nerve.  The  front  part  of  the  ver- 
tical plate  fits  along  the  inner  wall  of  the  antrum  of  the  superior  maxilla,. 

and  helps  to  close  the  lower  and  back  part  of  the  orifice  of  the  antrum. 
6 


82  HUMAN   OSTEOLOGY. 

This  part,  however,  is  very  fragile,  and  is  generally  broken  in  separating 
the  bones. 

Tuberosity. — From  the  angle  formed  by  the  horizontal  and  vertical 
plates  projects  backward  what  is  called  the  '  tuberosity/  This  is  the 
thickest  and  strongest  part  of  the  whole  bone,  and  it  fits  into  and  fills  up 
the  '  notch '  which  is  seen  between  the  pterygoid  plates  of  the  sphenoid. 
Notice  also  that  its  posterior  aspect  presents  a  groove  which  completes 
the  pterygoid  fossa,  and  gives  origin  to  a  part  of  the  '  pterygoideus  inter- 
nus/  The  groove  is  bounded  by  two  rough  surfaces,  which  diverge  from 
•each  other  like  the  letter  V  reversed,  and  fit  into  the  borders  of  the  notch 
itself.  (Plate  X.  Fig.  2.)  The  anterior  aspect  of  the  tuberosity  presents 
•&  very  rugged  surface,  which  articulates  with  th3  cuberosity  of  the  supe- 
rior maxillary  bone.  Behind  this  rough  surface  is  a  smooth  portion  con- 
tinuous with  the  plane  of  the  external  pterygoid  plate;  this  smooth  part 
gives  origin  to  some  of  the  fibres  of  the  external  pterygoid  muscle.  The 
inferior  aspect  has  nothing  remarkable  on  it,  except  the  orifices  of  one  or 
two  canals  large  enough  to  admit  a  pin.  They  are  the  '  accessory  palatine 
canals/  and  transmit  the  external  and  the  small  palatine  nerves  to  the 
soft  palate. 

Turn  now  your  attention  to  the  upper  part  of  the  palate  bone,  and  ob- 
serve that  at  the  top  of  the  vertical  plate  there  are  two  processes  separated 
by  a  deep  notch,  which  forms  the  greater  part  of  the  '  spheno-palatine 
foramen/  One  of  these  processes  is  called  the  '  orbital/  because  it  fills 
up  a  little  corner  at  the  back  part  of  the  orbit;  the  other  is  called  the 
'  sphenoidal/  because  it  fits  under  the  body  of  the  sphenoid  bone. 

Orbital  Process. — The  '  orbital  process'  springs  from  the  top  of  the 
hone  by  a  narrow  '  neck/  and  is  hollow,  so  that  it  forms  a  cell.  The  cell 
contains  air,  admitted  through  one  of  the  posterior  ethmoidal  cells.  This 
little  process  1n.asjive  surfaces,  unequal  in  extent,  and  looking  in  different 
directions.  If  you  hold  the  bone  before  you,  precisely  as  it  is  in  your  own 
person,  and  remember  that  it  is  interposed  between  the  maxillary  in  front 
and  the  sphenoid  behind,  you  will  have  no  difficulty  in  recognizing  the 
direction  of  the  surfaces  to  be  as  follows  (see  Plate  XIII.  Fig.  2) : — the 
superior  looks  into  the  orbit  and  contributes  to  form  its  floor;  the  external 
looks  into  the  spheno-maxillary  fossa;  the  posterior  is  connected  with  the 
body  of  the  sphenoid;  the  internal  with  the  ethmoid;  and  the  anterior 
with  the  superior  maxillary  bone.  Thus,  then,  we  have  a  superior  or 
orbital  surface,  an  external  or  zygomatic,  a  posterior  or  sphenoidal,  an  in- 


PALATE   BONE.  83 

ternal  or  ethmoidal,  and  an  anterior  or  maxillary:  of  these  five  two  only 
are  free,  namely,  the  orbital  and  the  zygomatic — the  other  three  are  at- 
tached to  the  respective  bones  with  which  they  are  contiguous.  Plate 
XXII.  shows  the  little  corner  at  the  inner  and  back  part  of  the  orbit,  which 
is  filled  up  by  the  palate  bone,  and  also  the  relative  positions  of  the  bones 
with  which  the  orbital  process  is  connected.  It  likewise  shows  that  the 
'  zygomatic  surface '  forms  that  part  of  the  floor  of  the  spheno-maxillary 
fossa  which  lies  above  the  spheno-palatine  foramen. 

Sphenoidal  Process. — The  'sphenoidal  process 'is  a  thin  plate  of 
bone,  which  arches  inward  beneath  the  body  of  the  sphenoid,  and  forms 
part  of  the  roof  of  the  nasal  fossa.  As  it  is  generally  broken  in  the  sepa- 
rate bone,  one  can  see  it  best  in  the  perfect  skull.  (Plate  XX.)  The 
arch  which  it  forms  has  three  surfaces, — an  upper  or  convex  surface, 
which  closes  in  the  pterygo-palatine  canal;  an  under  or  concave  surface, 
which  is  seen  in  looking  into  the  nasal  fossa;  and,  lastly,  an  outer,  which 
is  seen  in  looking  at  the  bottom  of  the  spheno-maxillary  fossa. 

Spheno-Palatine  Foramen. — Respecting  the '  spheno-palatine  fora- 
men/ we  need,  for  the  present,  merely  observe,  that  it  is  an  opening 
which  leads  from  the  spheno-maxillary  fossa  into  the  cavity  of  the  nose, 
and  transmits  the  nasal  or  spheno-palatine  branch  of  the  internal  maxil- 
lary artery  and  nasal  branches  of  the  spheno-palatine  ganglion.  (Plate 
XXII.) 

Connections. — The  palate  bone  articulates  with  six  bones, — namely, 
its  fellow,  the  sphenoid,  the  ethmoid,  the  inferior  spongy  bone,  the  vo- 
mer,  and  the  superior  maxilla. 

Ossification. — It  is  developed  from  a  single  centre  of  ossification, 
which  appears  at  the  angle  of  the  horizontal  and  vertical  portions,  about 
the  seventh  week  of  f oetal  life. 

Right  or  Left? — This  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body  if  he  hold  the  notch  (which  forms 
with  the  sphenoid  the  spheno-palatine  foramen)  upward,  the  orbital 
process  forward,  and  the  palatine  plate  inward. 


84  HUMAN    OSTEOLOGY. 

INFERIOR  SPONGY  OR  TURBINATED  BONE. 
(PLATE  XV.  Figs.  1  and  8.) 

In  each  nasal  cavity  there  are  three  spongy  or  turbinated  bones — an 
upper,  a  middle,  and  a  lower.  The  upper  and  middle  form  part  of  the 
ethmoid  bone,  and  have  been  already  described,  p.  73.  We  have  now  to 
examine  the  lower  one. 

Its  Position  and  Use. — This  thin  plate  of  bone  is  well  called 
'  spongy,'  from  its  structure,  and  '  turbinated/  from  its  curved  form.  By 
referring  to  Plate  XXIII.  Fig.  2,  you  see  it  in  situ,  and  observe  how  much 
longer  it  is  than  either  of  the  others.  Its  internal  surface,  forming  the 
convex  part  of  the  roll,  looks  toward  the  septum  of  the  nose;  its  external 
surface  forms  the  concave  part,  and  bounds  the  inferior  meatus  of  the 
nose.  Both  surfaces  are  covered  with  little  ridges  and  furrows,  and  more 
or  less 'horizontal  canals,  which  lodge  numerous  plexuses  of  arteries,  but 
chiefly  of  veins.  This  quite  accords  with  the  function  served  by  the 
bone,  namely,  of  affording  an  additional  extent  of  surface  which  warms 
the  air  on  its  passage  to  the  lungs.  It  has  nothing  to  do  with  the  sense 
of  smell.  The  olfactory  nerves  have  not  been  traced  lower  than  the  mid- 
dle spongy  bone. 

Connections. — By  its  upper  edge  it  is  attached  along  the  outer  wall 
of  the  nose  to  four  bones  as  follows — Beginning  from  the  front,  we  find 
it  attached,  1,  to  a  ridge  along  the  nasal  process  of  the  superior  maxilla; 
2,  by  means  of  a  little  '  tongue '  ('  lachrymal  process ')  to  just  such  another 
'  tongue '  of  the  lachrymal;  it  is  this  part  of  the  bone  which  completes  the 
lachrymal  canal;  3,  to  the  orifice  of  the  antrum  by  means  of  a  triangular 
plate  termed  the  'maxillary  process'  (Plate  XV.  Fig.  3,)  which  turns 
down  like  a  dog's  ear,  and  helps  to  narrow  the  lower  part  of  the  orifice  of 
the  antrum;  4,  to  the  unciform  plate  of  the  ethmoid  by  means  of  a  little 
tongue,  called  the  'ethmoidal  process' ;  5,  and  lastly,  to  a  ridge  along  the 
vertical  plate  of  the  palate  bone.  Notwithstanding  these  numerous  con- 
nections, the  bone  is  by  no  means  strongly  fixed  in  its  position:  in  the 
dry  skull  it  often  falls  out;  and  in  the  operation  of  extracting  a  polypus 
from  the  nose,  it  is  quite  possible  to  pull  out  part  of  the  bone  or  even  the 
entire  bone  with  the  polypus. 

Its  lower  edge  is  free,  and  generally  about  half  an  inch  from  the  floor 


Lachrymal  process 


....Ethmo\dal  process. 

Eift.1. 

In  Peri  DP  Spongy  tone,  inner  surface. 


Lachrymal  bono 


Inferior  Sponhy  bone,  outer  surface. 


Groove  For  Naso-palatine  iierve 


VOMER 


Temporal 


ly^ornatic. 

•fossa  .j^... 


\  Ft&2' 


Sphenoidal  F  issure  /    Palate  "bone,  '^Ethmoid  boneXLachry 


Crest 


Groove  for  naiss3  nerv/e. 


MASAL  BONE. 


Posterior  view. 


Anterior  view. 


THE    VOMER.  85 

of  the  nose,  so  that  there  is  just  room  enough  to  introduce  the  tube  of  a 
stomach-pump  through  the  nose. 

Ossification. — The  bone  has  one  independent  centre  of  ossification, 
which  appears  about  the  fifth  month  of  total  life. 

Right  or  Left  ? — This  bone  will  be  in  the  same  position  as  the  corre- 
sponding one  in  the  student's  body  if  he  hold  the  convex  surface  inward 
toward  the  septum  of  the  nose;  the  maxillary  process  hanging  downward; 
and  the  large  lachrymal  process  in  front  of  the  smaller  ethmoidal  process. 

Comparative  Osteology. — See  the  remarks  at  the  end  of  'the 
Ethmoid  bone.' 


THE    VOMER. 
(PLATE  XVI.  Fig.  1.) 

The  '  vomer*  is  so  named  from  its  resemblance  to  a  ploughshare.  It  is 
a  thin  and  delicate  plate,  situated  perpendicularly  in  the  middle  line,  and, 
together  with  the  perpendicular  plate  of  the  ethmoid  bone,  forms  the 
bony  septum  of  the  nose.  (Plate  XXIII.  Fig.  1.) 

Two  Plates. — Thin  as  it  is,  the  vomer  consists  of  two  plates,  united 
in  the  middle,  but  separated  above,  where  they  become  stronger,  diverge 
from  each  other,  and  form  a  deep  fissure  which  receives  the  '  rostrum ' 
of  the  sphenoid.  The  diverging  edges  of  the  fissure,  called  the  '  wings/ 
fit  into  the  little  furrows  beneath  the  '  vaginal  processes '  of  the  sphenoid. 
(Plate  XI,  Fig.  1.)  Concerning  the  other  connections  of  the  vomer,  we 
hav.e  to  observe  that  the  two  plates  of  which  the  bone  is  composed  sepa- 
rate from  each  other  at  every  articular  edge  of  it;  and  as  the  vomer  receives 
the  other  bones  into  its  grooves,  so  it  is  locked  in  on  all  sides. 

Connections. — The  vomer  is  connected  with  six  bones.  Below,  it 
articulates  with  the  crest  of  the  maxillary  and  palate  bones;  above,  with 
the  lower  edge  of  the  rostrum  of  the  sphenoid;  in  front,  with  the 
perpendicular  plate  of  the  ethmoid,  and  the  median  cartilage  of  the  nose; 
behind,  its  edge  is  sharp  and  free,  and,  in  the  perfect  skull,  is  seen  as  the 
septum  between  the  posterior  openings  of  the  nasal  fossae. 

Both  surfaces  of  the  vomer  are  marked  by  grooves  for  blood-vessels 
and  nerves:  but  the  only  groove  deserving  notice  is  that  which  descends 
obliquely  and  transmits  the  '  naso-palatine  nerve.' 


86  HUMAN   OSTEOLOGY. 

It  is  necessary  to  know  that  the  direction  of  the  vomer  is  not,  in  all 
persons,  perpendicular.  In  100  skulls  the  vomer  was  found  to  be  perpen- 
dicular only  in  24.  There  are  instances  in  which  it  projects  into  one 
side  of  the  nose  to  such  an  unusual  extent,  that  when  covered  by  its  vascu- 
lar and  swollen  mucous  membrane,  the  projection  might  easily  be  mis- 
taken for  a  polypus.  Such  mistakes  are  alluded  to  in  surgical  works. M 

Ossification. — The  vomer  is  developed  from  one  center  of  ossifica- 
tion, which  appears  about  the  seventh  week  of  foetal  life,  at  the  upper 
part,  and  from  it  each  lateral  plate  is  developed. 


THE  INFERIOR  MAXILLARY  BONE. 

(PLATE    XVII.) 

For  convenience  of  description  we  divide  the  lower  jaw  into  the  arched 
part  in  front,  the  '  body/  and  the  ascending  part  behind,  the  '  ramus.'  At 
the  top  of  each  ramus  are  the  '  condyle  '  or  articular  surface,  the  '  coro- 
noid '  process  for  the  insertion  of  the  temporal  muscle,  and  the  '  sigmoid 
notch/ 

Body  and  Symphysis. — The  convex  part  of  the  body  presents,  ex- 
actly in  the  center,  a  slight  ridge,  the  '  symphysis/  which  is  the  strongest 
part  of  the  bone,  and  indicates  where  the  two  halves  of  the  bone  grew 
together.  Its  direction  is  vertical,  or  even  projects  forward:  this  is  one 
of  the  characteristics  of  man,  who  alone  has  a  chin.  The  '  symphysis ' 
terminates,  below,  in  the  triangular  '  mental  process/  On  each  side  of 
the  symphysis  is  a  slight  depression,  the  '  mental  fossa/  which  gives 
origin  to  the  'levator  menti/  More  externally,  and  generally  in  a  line 
with  the  first  prae-molar  tooth,  is  the  '  mental  foramen/  which  transmits 
the  '  mental  branch '  of  the  inferior  dental  nerve  and  artery.  From  the 
lower  part  of  the  symphysis  we  trace  the  beginning  of  the  '  external 
oblique  line  '  or  ridge,  which  curves  backward  toward  the  root  of 
the  coronoid  process.  This  line  gives  origin  to  the  '  depressor  labii  in- 
ferioris  '  and  '  depressor  anguli  oris/  A  little  below  both  these,  is  the 
insertion  of  the  '  platysma-myoides '  of  the  neck.  Along  the  alveolar 
border  adjacent  to  the  three  molar  teeth  is  one  origin  of  the  '  buccinator/ 

Four  Tubercles. — On  the  concave  surface  of  the  body  (Fig.  2),  at 

M  Jarjavay,  'Anatomie  Chir.'  t.  ii.  p.  61. 


PLATE  XVII. 


B&.l. 


ro^oid  process, 
sertion  cf  fcetDporcdis 


External  obfiqCte  line. 


Mylo-ViyoicJ  ri 
"SituaHon  fcr  Sublin^ua]  ^land 


Tubercle  -for  Qer.io-liyo-^ossus. 
Tubercle  for  Genio-V.yoitleus, 


THE    INFERIOR   MAXILLARY    BONE.  87 

the  symphysis,  are  four  small  tubercles,  i.e.  two  on  each  side,  one  above 
the  other;  the  upper  give  origin  to  the  '  genio-hyoglossi':  the  lower,  to 
the  '  genio-hyoidei.'  These  four  tubercles  in  some  instances  are  conflu- 
ent, and  appear  as  one.  Beneath  these  is  a  well-marked  depression  on 
each  side,  for  the  insertion  of  the  '  digastricus'  muscle,  which  opens  the 
mouth.  On  this  surface  is  an  oblique  line,  faint  near  the  symphysis,  but 
more  prominent  as  it  ascends  backward  below  the  last  molar  tooth.  It 
is  called  the  '  mylo-hyoid  ridge/  because  it  gives  origin  to  the  '  mylo- 
hyoideus.'  Behind  and  a  little  above  this  ridge,  near  the  last  molar 
tooth,  is  the  origin  of  part  of  the  '  superior  constrictor '  of  the  pharynx. 
Below  the  ridge  is  a  slight  depression,  indicating  the  position  of  the  sub- 
maxillary  salivary  gland.  Above  the  ridge  is  the  place  for  the  sub-lingual 
gland;  but  this  is  not  well  marked. 

Oblique  Lines. — These  oblique  lines  or  ridges  on  the  two  surfaces 
of  the  body  are  something  more  than  mere  muscular  impressions.  They 
indicate  the  limit  between  the  '  alveolar '  part  which  contains  the  teeth, 
and  the  lower  or  '  basilar '  part  of  the  jaw.  These  distinctions  are  made 
because  these  parts  come  and  go  at  different  periods  of  life.  In  infancy 
there  is  only  the  alveolar  part;  toward  puberty  the  basilar  part  slowly 
grows  to  perfection:  in  old  age  when  the  teeth  fall  out,  aad  their  sockets 
are  absorbed,  the  basilar  part  alone  remains,  and  the  chin  gradually  ap- 
proximates the  nose.  The  absorption  of  the  sockets  (alveoli),  which  is 
natural  in  old  persons,  often  occurs  prematurely.  It  is  apt  to  arise  from 
long  salivation,  scurvy,  or  purpura,  and  is  frequently  hereditary. 

Teeth. — The  teeth  in  the  lower  jaw  correspond  in  number  (eight  on 
each  side)  with  those  in  the  upper,  but  differ  from  them  in  these  par- 
ticulars:— 1.  The  first  two  lower  molars  have  only  two  fangs,  an  anterior 
and  posterior,  while  the  upper  molars  have  three.  In  the  third  molar  or 
wisdom  tooth  the  fangs  are  often  consolidated  into  one;  2.  When  the 
mouth  is  closed  the  teeth  of  the  lower  jaw  shut  within  those  of  the  upper 
jaw  which  form  a  larger  arch;  3.  The  external  tubercles  or  cusps 'of  the 
teeth  of  the  lower  jaw  fit  into  the  hollows  between  the  external  and 
internal  cusps  of  the  teeth  of  the  upper  jaw;  by  which  arrangement  we 
are  enabled  to  use  the  entire  surface  of  the  opposing  teeth  in  grinding 
the  food.  When  the  jaws  are  closed,  each  tooth  in  one  jaw  is  opposed 
by  two  in  the  opposite  jaw;  one  good  result  of  this  is,  that  when  we  lose 
a  tooth,  the  corresponding  tooth  in  the  other  jaw  being  still  more  or  less 
opposed,  is  still  of  service  in  mastication. 


88  HUMAN    OSTEOLOGY. 

Ramus. — The  ramus  of  the  jaw  mounts  up  from  the  body  nearly  at 
a  right  angle  in  adult  age,  when  the  upper  and  lower  jaws  are  kept  well 
apart  behind  by  the  molar  teeth.  But  in  infancy,  before  the  develop- 
ment of  the  molars,  and  in  age  when  they  are  lost,  the  '  angle'  of  the  jaw 
becomes  obtuse.  Excluding  its  outstanding  processes,  the  ramus  is  nearly 
square.  Nearly  the  whole  of  its  outer  surface  gives  insertion  to  the 
powerful  '  masseter,'  which  closes  the  jaw  (Fig.  1).  On  its  inner  sur- 
face (Fig.  2)  is  the  '  dental  foramen/  or  the  orifice  of  the  canal  for  the 
transmission  of  the  inferior  dental  nerve  and  artery.  Its  inner  margin  is 
raised  into  a  short  '  spine '  for  the  attachment  of  the  internal  lateral  lig- 
ament of  the  jaw.  Leading  down  from  the  orifice  is  the  '  mylo-hyoid 
groove/  which  contains  the  mylo-hyoidean  vessels  and  nerve.  Below  the 
groove  is  the  rough  surface  for  the  insertion  of  the  '  pterygoideus  in- 
ternus/  The  muscles  inserted  on  each  surface  of  the  angle  of  the  jaw 
are  so  thick  that  fractures  through  this  part  of  the  bone  sometimes  es- 
cape detection. 

Condyle. — The  '  condyle '  projects  from  the  upper  and  back  part  of 
the  ramus  to  form  the  joint  of  the  jaw,  and  fits  into  the  glenoid  cavity  of 
the  temporal  bone.  It  is  oblong  in  form,  and  convex  both  from  without 
inward  and  from  before  backward.  The  long  axis  is  directed  horizontally 
inward  and  slightly  backward,  so  that,  if  prolonged,  the  axes  of 
the  two  condyles  would  meet  near  the  front  of  the  '  foramen  magnum/ 
Just  outside  the  condyle  is  a  '  tubercle  '  for  the  attachment  of  the  ex- 
ternal lateral  ligament.  The  condyle  is  supported  on  a  contracted  part 
termed  the  '  neck '  of  the  jaw.  This  neck  is  flattened  in  the  same  direc- 
tion as  the  condyle,  and  is  slightly  excavated  in  front  for  the  insertion 
of  the  '  pterygoideus  externus/ 

The  oblique  direction  of  the  condyles  of  the  jaw  renders  easy  the 
rotatory  movement  necessary  in  mastication.  In  masticating  we  can 
readily  feel  that  one  condyle  advances  toward  the  anterior  margin  of  its 
glenoi'd  cavity,  while  the  other  recedes  to  the  posterior. 

Coronoid  Process. — The  '  coronoid '  process  is  a  triangular,  lofty 
plate  of  bone,  which  ascends  beneath  the  zygomatic  arch  and  increases 
the  leverage  of  the  temporal  muscle  which  closes  the  mouth.  The  inser- 
tion of  this  muscle  occupies  the  inner  surface,  the  apex,  and  front  border 
of  the  process  down  to  the  last  molar  tooth:  the  greater  part  of  the  outer 
surface  is  occupied  by  the  masseter.  The  '  sigmoid  notch '  transmits  the 
'  masseteric '  nerve  and  artery. 


THE    INFERIOR    MAXILLARY    BONE.  89 

The  walls  of  the  lower  jaw,  particularly  at  the  basilar  part,  are  exceed- 
ingly compact  and  tough.  In  operations  for  removal  of  this  part  of  the 
bone,  it  is  necessary  to  use  the  saw  freely,  before  the  bone  forceps  can  be 
of  any  service.  The  interior  assumes  the  form  of  '  diploe/  and  is  tra- 
versed by  the  '  inferior  dental  canal/  which  carries  the  vessels  and  nerves 
to  the  teeth  (Nor.  Hum.  Ost.  No.  234).  This  canal  begins  on  the  inner 
side  of  the  ramus,  curves  forward,  beneath  the  sockets  of  the  teeth,  and, 
toward  the  front,  divides  into  two,  of  which  one  ends  at  the  '  foramen 
mentale/  the  other,  much  diminished  in  size,  runs  on  through  the  diploe 
nearly  to  the  symphysis,  and  conveys  vessels  and  nerves  to  the  canine  and 
incisor  teeth. 

Ossification. — The  lower  jaw  has  two  centres  of  ossification,  which 
appear  about  the  sixth  week  of  foetal  life,  one  for  each  lateral  half.  Their 
junction  at  the  symphysis  takes  place  about  the  close  of  the  first  year 
after  birth.  In  the  lower  animals  the  symphysial  suture  often  remains 
throughout  life." 

Comparative  Osteology. — In  the  order  Monotremata,  observe  that 
there  is  scarcely  any  bend  or  inflexion  in  the  lower  jaw  (No.  1699).  The 
jaw  of  the  ant-eater  is  also  straight,  thus  greatly  resembling  that  of  the 
pelican  (see  Sep.  Ser.). 

In  snakes  (Ophidia)  the  two  halves  of  the  lower  jaw  are  not  united 
by  bone,  but  held  together  by  an  elastic  ligament,  which  permits  the  two 
halves  of  the  jaw  to  be  separated  from  each  other  sideways  to  a  consider- 
able extent.  This  is  one  of  the  many  arrangements  by  which  the  boa  is 
enabled  to  swallow  its  prey  though  larger  than  its  own  body.  This  is 
shown  in  the  specimen  of  the  tiger-boa  (No.  602). 

In  the  lower  animals  the  two  halves  of  the  jaw  generally  remain  sepa- 
rate throughout  life.  In  all  mammalia  each  half  of  the  lower  jaw  consists 
of  a  single  piece  which  articulates  with  the  squamosal  bone  of  the  skull. 
In  all  below  the  mammals  it  articulates  with  a  modified  malleus  called 
the  quadrate  bone.  This  is  well  seen  in  the  skull  of  the  ostrich  and  other 
birds  in  the  Separate  Series. 

[For  some  interesting  points  as  to  the  relation  between  the  size  of  the 
coronoid  process  and  the  temporal  fossa  the  student  should  read  the  Com- 
parative Osteology  paragraph  at  the  end  of  the  chapter  on  '  The  Skull  as 
a  Whole.'] 

65  For  a  lucid  and  elaborate  account  of  the  development  of  the  jaws  and  the  teeth 
see  '  Manual  of  Dental  Anatomy, '  by  C.  S.  Tomes,  M.  A.  1876. 


90  HUMAN    OSTEOLOGY. 

It  has  been  said  that  man  is  the  only  creature  which  has  a  chin.  It 
is  most  distinct  in  the  Caucasian  race,  becomes  faintly  marked  in  the 
Negro,  and  does  not  exist  in  the  Apes. 

Rodentia  have  never  more  than  two  incisors  in  the  lower  jaw;  and 
usually  only  two,  but  sometimes  four,  in  the  upper.  When  there  are  four 
incisors  in  the  upper  jaw,  as  in  hares  and  rabbits,  there  are  two  small 
ones  behind  the  two  large  ones  (No.  1916).  These  incisors  have  a  persist- 
ent pulp,  and  continue  to  grow  in  adult  life.  They  have  no  canines. 

Carnivora  have  milk  and  permanent  teeth,  which  are  enamelled,  and 
always  consist  of  incisors,  canines,  and  molars. 

In  elephants  the  teeth  consist  of  tusk-like  incisors,  growing  from  per- 
sistent pulps,  and  molars. 

Look  at  the  lower  jaw  of  the  crocodile  (No.  717  D)  and  see  how  greatly 
the  angle  projects  backward.  This  projection  is  for  the  insertion  of  the 
digastricus,  the  muscle  which  opens  the  mouth,  and  which  acts  upon  the 
jaw  as  a  lever  of  the  first  order.  In  man  it  acts  as  a  lever  of  the  second 
order,  as  it  is  inserted  near  the  symphysis. 

To  appreciate  the  mechanism  of  the  lower  jaw,  look  at  the  form  of  the 
joint  in  animals.  In  them  it  varies  according  to  the  structure  of  their 
teeth  and  the  food  they  eat.  There  are  three  principal  types  of  it:  the 
carnivorous,  the  ruminant,  and  the  rodent.  The  carnivorous  type  is  a 


<? 
FIG.  18.  FIG.  19. 

simple  transverse  hinge:  this  form  is  well  seen  in  the  badger  (No.  4412), 
where  the  condyle  of  the  jaw  is  mechanically  locked  in  its  socket.  It  is 
shown  in  Fig.  17,  where  G-  represents  the  shape  of  the  glenoid  cavity,  and 
C  the  shape  of  the  condyle  which  fits  into  it.  The  ruminant  type  pre- 
sents a  socket  and  a  condyle  nearly  flat,  so  as  to  admit  of  the  lateral 
movement  necessary  for  grinding  the  food.  This  form  is  seen  in  Fig.  18, 
which  is  taken  from  the  sheep  (No.  3767  B).  In  the  rodent  type  there  is 
a  longitudinal  groove  in  the  temporal  bone  in  which  the  condyle  plays 
from  before  backward  like  a  plane.  Fig.  19  shows  the  corresponding  sur- 


THE    INFERIOR   MAXILLARY    BONE.  91 

faces  of  the  glenoid  cavity  (Gr),  and  the  condyle  (C),  in  the  capybara  (No.. 
1974). 

The  joint  of  the  lower  jaw  in  man  partakes  somewhat  of  the  nature 
of  these  three  types:  we  can  move  our  jaw  in  the  vertical  direction,  from 
side  to  side,  and  from  before  backward.  The  teeth  of  man  are  likewise 
intermediate  in  structure  between  those  of  carnivorous  and  those  of 
ruminant  animals.  Man  is  adapted,  by  his  dentition,  to  eat  animal  or 
vegetable  food,  and  is  said  to  be  omnivorous.  But  the  presence  of  grind- 
ing, tearing,  and  cutting  teeth,  equally  developed,  in  the  jaws  of  any 
animal,  is  no  proof  that  he  is  omnivorous.  Monkeys  have  large  canines, 
yet  live  on  vegetables;  all  bats  possess  well-formed  incisors,  canines,  and 
molars,  yet  some  are  purely  frugivorous,  whilst  the  British  species  live 
entirely  on  insects. 


THE  SKULL  AS  A  WHOLE. 

THE  examination  of  the  Skull  as  a  whole  is  easy  and  intelligible,  provided 
the  individual  bones  have  been  carefully  studied. 

Course  of  Sutures. — A  knowledge  of  the  course  of  the  sutures  is 
of  practical  value — 1,  because  it  enables  us  to  say  with  precision  in  what 
direction  the  head  of  the  child  is  presenting  during  labor;  2,  because  in 
injuries  of  the  skull  we  must  not  commit  the  error  of  mistaking  a  suture 
for  a  fracture." 

Coronal  Suture. — The  *  coronal  suture'  (Plate  XVIII.)  (fronto-pa- 
rietal)  connects  the  frontal  with  the  parietal  bones.  It  extends  trans- 
versely across  the  top  of  the  skull,  from  the  great  wing  of  the  sphenoid 
on  one  side  to  the  other.  In  the  middle  the  frontal  overlaps  the  parietal 
bones,  but  at  the  sides  the  parietals  overlap  the  frontal,  by  which  arrange- 
ment the  bones  are  locked  together. 

Sagittal  Suture. — The  'sagittal  suture'  (inter-parietal)  connects 
the  two  parietal  bones.  It  runs  backward,  in  the  middle  line,  from  the 
frontal  to  the  occipital  bone.  This  suture  is  much  serrated,  except  near 
the  parietal  foramina,  where  it  is  always  much  straighter  than  elsewhere. " 

Frontal  Suture. — The  'frontal  suture 'is  formed  by  the  union  of 
the  two  halves  of  the  frontal  bone.  It  runs  down  the  middle  of  the  fore- 
head, from  the  sagittal  suture  to  the  root  of  the  nose.  It  always  exists 
in  infancy  and  childhood,  but  is  generally  obliterated  in  the  adult  (p.  51). 

Lambdoid  Suture. — The  '  lambdoid  suture '  (Greek  letter  A)  (oc- 
cipito-parietal)  unites  the  two  parietals  to  the  occipital  bone. 

66  Skilful  as  he  was,  Hippocrates  once  mistook  a  natural  suture  of  the  skull  for  a 
fracture,  and  was  afterward  so  ingenuous  as  to  leave  his  mistake  on  record.  On  this, 
Celsus  observes:  'A  suturis  se  deceptnm  esse  Hippocrates  memoriae  prodidit,  more 
scilicet  magnorum  virorum  et  fiduciam  magnarum  rerum  habentium.  Nam  levia 
ingenia,  quia  nihilhabent,  nihil  sibi  detrahunt:  magno  ingenio,  multaque  nihilominus 
habituro,  convenit  etiam  simplex  veri  errorisconfessio;  prsecipueque  in  eo  ministerio 
quod  utilitatis  causS  posteris  traditur  neque  decipiantur  eadem  ratione,  quS  quis  antd 
deceptus  est.'  (Liber  viii.  cap.  iv.) 

61  Broca,  '  Osteologie  du  Crane,'  1875. 


PLATE  XVIII. 


t  al      BOT 


n  e 


PLATE  XVIII" 


Pig.  8. 


life  . 


Anterior  FortoneVle. 


Lateral  fontanell 


Posterior  fontanelle. 


Fatal  slxullftilltprm, 


Tympanic  bone- 
Foetal  s\ull  Full  term. 


THE   SKULL   AS   A   WHOLE.  93 

Occipito-Mastoid  Suture.  —  '  The  occipito-mastoid  suture/  " 
apparently  a  continuation  of  the  lambdoid,  connects  the  occipital  with 
the  mastoid  portion  of  the  temporal  bone. 

Masto-Parietal  Suture. — The  mastoid  part  of  the  temporal  is  con- 
nected to  the  posterior  inferior  angle  of  the  parietal  bone  by  the  '  masto- 
parietal  suture.' 

Squamous  Suture. — The  squamous  part  of  the  temporal  is  con- 
nected to  the  parietal  bone  by  the  '  squamous  suture '  (squamo-parietal) ; 
and  to  the  great  wing  of  the  sphenoid  by  the  '  squamo-sphenoidal '  suture. 
The  squamous  bone  so  overlaps  the  parietal  as  to  strengthen  the  arch  of 
the  skull  at  the  sides,  and  prevent  the  lateral  expansion  of  the  buttresses. 

Wormian  Bones. — In  the  mastoid  suture  more  frequently  than  in 
any  other,  we  meet  with  what  are  termed  '  Wormian  M  bones,'  or  '  ossa 
triquetra.'  They  are  little  islands  of  bone,  developed  from  distinct  cen- 
tres, in  the  membrane  which  connects  the  cranial  bones.  They  vary  in 
number  and  size.  In  the  Museum  of  the  College  of  Surgeons  there  is  the 
hydrocephalic  skull  of  an  adult  (Path.  Ser.  No.  3489)  in  which  there 
are  upward  of  one  hundred  of  these  little  bones.  Specimens  of  Wormian 
bones  may  be  seen  in  the  Gen.  Ost.  Ser.  Nos.  103  to  110. 

Transverse  Frontal  Suture. — Of  the  sutures  which  connect  the 
bones  of  the  cranium  with  the  face,  the  chief  one  is  the  '  transverse  frontal 
suture.'  It  extends  from  the  external  angular  process  of  the  frontal  bone, 
from  one  side  to  the  other,  across  both  orbits  and  the  root  of  the  nose 
(Plate  XVI.).  It  connects  the  frontal  with  the  malar,  sphenoid,  eth- 
moid, lachrymal,  superior  maxillary,  and  nasal  bones.  Other  short  su- 
tures, such  as  the  '  spheno-malar,'  '  spheno-parietal,'  '  zygomatic,'  etc., 
speak  for  themselves. 

A  knowledge  of  the  sutures  is  of  practical  value  in  midwifery.  Thus 
when  we  feel  the  meeting  of  the  three  sutures  at  the  top  of  the  occipital 
bone,  Ave  know  the  back  of  the  head  presents;  if,  again,  we  feel  the  'an- 
terior fontanelle,'  or  lozenge-shaped  space  where  four  sutures  meet  (page 
44),  we  know  it  is  a  forehead  presentation. 

58  The  old  anatomists  call  this  the  '  additamentum  suturae  lambdoidalis. '  This 
old  name  as  well  as  others  mentioned  in  the  text,  e.g.  'coronal,'  'sagittal,'  and  '  lamb- 
doid,' are  gradually  falling  into  disuse,  and  giving  place  to  more  appropriate  terms, 
derived  from  the  bones  connected,  as  '  inter-parietal,'  '  f ronto-parietal, '  etc. 

59  So  called  after  Olaus  Wormius,  a  physician  of  Copenhagen,  to  whom  the  first 
description  of  these  '  complementary  '  bones  has  been  assigned,— but  erroneously: 
they  were  known  to  Eustachius  and  Paracelsus. 


94  HUMAN    OSTEOLOGY. 


THE    SKULL-CAP. 

Skull-cap:  Outer  Surface. — The  skull-cap  forms  an  oval  dome 
which  protects  the  brain  with  its  greatest  breadth  about  the  parietal  pro- 
tuberances. In  a  well-formed  European  head,  if  we  look  at  the  skull-cap 
from  above  (the  beginning  of  the  sagittal  suture  being  in  the  centre  of 
the  perspective  plane),  we  see  scarcely  anything  but  the  smooth  expanded 
vault  of  the  cranium.  But  in  the  Negro  and  the  Australian,  the  narrow- 
ness of  the  temples  allows  the  zygomata  to  come  into  view,  and,  in  the 
most  '  prognathous ' flo  examples,  the  incisor  teeth  appear  in  front  of  the 
frontal  sinuses. 

Foramina. — On  the  outer  surface  of  the  skull-cap  are  a  multitude  of 
small  foramina,  which  transmit  blood-vessels  from  the  pericranium  into 
the  substance  of  the  bonei  Hence,  if  this  membrane  be  torn  off  during 
life,  the  bone  bleeds  through  minute  pores.  On  each  side  of  the  sagittal 
suture  is  the  *  parietal  foramen/  which  transmits  a  vein  from  the  superior 
longitudinal  sinus  to  the  outside  of  the  skull;  sometimes  a  small  artery 
runs  with  it,  and  communicates  with  a  branch  of  the  middle  meningeal. 

Temporal  Ridge. — Along  the  side  of  the  skull-cap  is  a  curved  line, 
the  temporal  ridge  (Plate  XV.),  which  indicates  the  attachment  of  the 
temporal  aponeurosis  to  the  frontal  and  parietal  bones. 

Temporal  Fossa. — The  ridge  circumscribes  the  'temporal  fossa/ 
which  is  formed  by  the  frontal,  parietal,  temporal,  sphenoid,  and  malar 
bones.  The  fossa  gives  origin  to  the  temporal  muscle,  of  which  the  ten- 
dinous rays,  converging  beneath  the  zygoma,  are  inserted  into  the  coronoid 
process  of  the  lower  jaw.  The  size  of  the  temporal  fossa  in  all  animals 
depends  upon  the  size  of  the  temporal  muscle.  Hence  it  is  largest  in  the 
carnivora. 

Skull-cap:  Inner  Surface. — On  the  inner  surface  of  the  skull-cap 
we  observe — 1,  the  groove  in  the  middle  line,  which  gradually  becomea 
broader  as  we  trace  it  backward,  for  the  superior  longitudinal  sinus;  2, 
on  either  side  of  this,  especially  in  old  skulls,  are  a  number  of  irregular 
excavations,  occasioned  by  the  '  Pacchionian  bodies '; 81  3,  grooves  for  the 

eo  <  Prognathous  '  signifies  '  with  prominent  jaws. ' 

61  These  bodies  are  developed  from  the  '  arachnoid  '  or  serous  membrane  invest- 
ing the  brain,  beneath  the  '  dura  mater,'  which  they  perforate,  and  thus  come  to  press 
immediately  on  the  bony  vault  of  the  skull.  Vide  Quain's  '  Anatomy,'  vol.  ii.  p.  576, 
8th  edition. 


THE   SKULL    AS   A    WHOLE.  95 

ramifications  of  the  middle  meningeal  artery.  The  main  groove,  at  first 
sometimes  a  complete  canal,  is  seen  at  the  anterior-inferior  angle  of  the 
parietal  bone;  from  thence  it  spreads  widely  over  the  frontal  and  parietal 
bones,  one  branch  of  considerable  size  often  traversing  the  posterior-infe- 
rior angle  of  the  parietal  above  the  groove  for  the  lateral  sinus.  In  frac- 
tures of  the  skull,  the  arteries  running  in  these  grooves  are  liable  to  be 
injured,  and  thus  occasion  an  effusion  of  blood,  producing  compression  of 
the  brain. 

Thickness  of  the  Skull-cap. — The  s«£ull-cap  differs  in  thickness  in 
different  parts.  This  is  easily  ascertained  by  holding  it  to  the  light.  As 
a  rule,  it  is  thicker  in  parts  which  were  the  centres  of  ossification — as  at 
the  frontal  and  parietal  eminences.  It  is  thinnest  in  the  temporal  region. 
The  ordinary  thickness  of  an  adult  skull  is  about  one-fifth  of  an  inch, 
though  it  varies  very  much  at  different  periods  of  life.  In  the  anatomi- 
cal museum  at  Pavia  there  is  the  skull-cap  of  a  child,  in  which  a  hole  was 
pecked  /by  the  beak  of  an  angry  cock.  Whoever  is  in  the  habit  of  mak- 
ing post-mortem  examinations  soon  observes  how  much  skulls  vary  in 
thickness,  even  in  persons  of  the  same  age,  and  this  without  any  obvious 
reason.  Generally  speaking,  any  cause  which  produces  a  chronic  conges- 
tion of  the  vessels  of  the  head, — such  as  habits  of  intemperance, — will 
increase  the  thickness  of  the  skull.  For  the  same  reason  constant  ex- 
posure to  the  action  of  the  sun  will  thicken  and  indurate  the  skull-cap. 
The  observation  of  Herodotus"  is  probably  correct,  when  he  says  that 
*  the  Egyptians  have  thick  skulls  because  they  expose  their  shorn  heads 
to  the  heat  of  the  sun;  whereas  the  Persians  have  thin  and  soft  skulls 
because  they  cover  them  with  turbans  from  infancy.'  A  severe  blow 
may  thicken  the  skull.  The  late  Mr.  Quekett  had  in  his  possession  part 
of  a  skull-cap  nearly  an  inch  in  thickness.  It  belonged  to  a  gentleman 
who  received  a  blow  on  his  head  some  years  before  his  death.  He  recov- 
ered perfectly,  to  all  appearance,  from  the  effects  of  the  injury.  By- 
and-by,  however,  his  head  began  to  grow  larger;  but  this,  strange  to  say, 
was  first  discovered  by  his  hatter,  who  found  it  necessary  from  time  to 
time  to  give  him  a  larger  hat.  In  very  old  persons,  the  skull-cap,  owing 
to  the  absorption  of  the  diploe,  becomes  in  some  parts  as  thin  as  a  shil- 
ling. Not  only  the  skull,  but  all  the  bones  become  much  lighter  in  old 
age.  Soemmering  says  the  skull  of  a  centenarian  is  two-fifths  lighter 
than  in  middle  age. 

89  'Thalia,'  xii. 


96  HUMAN    OSTEOLOGY. 

Cerebral  Impressions. — The  inner  surface  of  the  skull-cap  is 
marked  by  the  cerebral  convolutions,  so  that  it  takes,  to  a  certain  extent, 
an  impression  of  the  brain.  But  it  cannot  be  said  that  a  particular  im- 
pression on  the  inner  surface  has  a  corresponding  bump  outside.  A 
glance  at  any  skull-cap  is  sufficient  to  prove  this.  The  depressions  occa- 
sioned by  the  convolutions  take  place  at  the  expense  of  the  diploe;  and 
the  external  bumps  are  often  caused  by  a  mere  thickening  of  the  outer 
table.  On  the  other  hand,  it  holds  good,  as  a  general  rule,  that  the 
external  form  and  dimensions  of  the  cranium  may  be  taken  as  a  general 
expression  of  the  corresponding  lobe  of  the  brain,  whether  in  the  frontal, 
the  parietal,  or  the  occipital  region.  The  general  characters  of  the 
brain,  then,  may  be  ascertained  by  external  examination,  but  not  the  indi- 
vidual detail. 

Veins  of  the  Diploe. — The  diploe  of  the  skull-cap  is  traversed  by 
numerous  venous  canals.  These  (Fig.  20)  are  of  considerable  size,  and  are 
best  displayed  by  filing  off  the  outer  table.  Their  course  is  by  no  means 


FIG.  20.— Venous  Canals  in  the  Diploe. 

so  regular  as  they  are  commonly  drawn;  but,  in  a  general  way,  we  may 
speak  of  the  frontal,  temporal,  and  occipital  '  diploic '  veins.  The  two 
former  discharge  their  blood  into  the  veins  on  the  outside  of  the  cranium; 
the  occipital  generally  open  into  the  lateral  sinus.  After  injuries  of  the 
head,  these  veins  are  liable  to  inflammation,  which  may  give  rise  to  pus  in 
the  diploe  and  pyaemia.  Hence  the  occasional  occurrence  of  visceral 
abscesses,  especially  hepatic,  after  injuries  of  the  head, — a  circumstance 
which  had  not  escaped  the  notice  of  the  old  surgeons. 


.Foramen 

.Groove  for  antr  men'm^ea!  artery 

..CrtotsL^ani. 

.$1  it  for  nasal  nerve, 

..Olfactory  canals  in  tVie 
OlFactory  groove . 


..  Spbenoidad  fissure  , 
..Tforameri  opt  v  cum. 
..Olivary  process  . 
.Anfc^clinoicl,  process, 
.  Pit^tary'fbp  ?n.  . 
."Fo  racmen.  rotundMtn  • 
•  -FostT  cli-no'tcl  proc  e  ss  . 
..Groove  for  caroVidarrery. 


.  Eoramen  lacerum  Toeclium  . 
..Foramen  ^pinosum, 


..Inf  T 

.."Meafcus  auditori\3S  mternus 
Acjueducbis  cocWese. 

posterius 


...  Ant1^  conclyloiol  foramen. 
..PostTcondyloid  foramen, 
...Sup^jetrosal  groove. 
..Mastxjicl  foramen.. 


...Groove  for  posterior. 
-  —  -•"  artery. 


..Groove for- .-lateral  s'mus. 
..Internal  occipital  prol'uW 


BASE  OF  THE  SKULL  AS  SEEN  FROM  ABOVE.        97 


BASE  OF  THE  SKULL  AS  SEEN  FROM  ABOVE. 

By  referring  to  Plate  XIX,  it  is  seen  that  the  base  of  the  skull  pre- 
sents, on  each  side,  three  fossae, — an  anterior,  a  middle,  and  a  posterior, 

respectively  lodging  the  anterior  and  middle  lobes  of  the  cerebrum,  and 

the  cerebellum.  The  posterior  lobe  of  the  cerebrum  rests  upon  the  '  ten- 
torium  cerebelli/  and  not  upon  bone.  These  several  fossae  are  marked 
by  the  cerebral  convolutions  just  as  much  as  the  skull-cap;  but  phrenolo- 
gists take  no  notice  of  these  convolutions,  and  have  omitted  to  assign 
any  office  to  them.  All  their  '  organs '  are  placed  at  the  top  and  sides  of 
the  brain; — why  are  there  none  at  the  base? 

Anterior  Fossa  of  the  Cranium. — The  anterior  fossa  of  the  cra- 
nium is  formed  by  the  orbital  plates  of  the  frontal,  the  cribriform  plate 
of  the  ethmoid,  with  the  front  part  of  the  body  and  the  lesser  wings  of 
the  sphenoid.  The  points  to  be  noticed  in  this  fossa  are  as  follows:  1. 
The  *  foramen  caecum/  which,  if  pervious,  generally  transmits  a  vein  from 
the  superior  longitudinal  sinus  into  the  nose.  2.  The  groove  for  the 
'  anterior  meningeal  artery,'  one  of  the  secondary  branches  of  the  ophthal- 
mic. 3.  The  '  crista  galli/  which  gives  attachment  to  the  falx  cerebri. 
4.  The  slit  for  the  '  nasal  nerve/  a  branch  of  the  first  division  of  the  fifth 
nerve.  5.  The  'olfactory  groove/  perforated  by  foramina,  which  give 
passage  to  the  filaments  of  the  olfactory  lobes.  6.  The  '  anterior  eth- 
moidal  foramen '  on  the  outer  side  of  the  olfactory  groove,  for  the  trans- 
mission of  the  nasal  nerve  and  anterior  ethmoidal  vessels.  7.  The  '  pos- 
terior ethmoidal  foramen/  at  the  hinder  extremity  of  the  olfactory  groove, 
immediately  in  front  of  the  body  of  the  sphenoid  transmits  the  posterior 
ethmoidal  vessels.  8.  The  '  foramen  opticum/  which  transmits  the  optic 
nerve  and  ophthalmic  artery.  9.  The  *  olivary  process,'  which  supports 
the  commissure  of  the  optic  nerves.  10.  The  'anterior  clinoid  process/ 
which  gives  attachment  to  the  tentorium  cerebelli. 

Middle  Fossa  of  the  Cranium. — The  middle  fossa  of  the  cranium 
supports  the  middle  cerebral  lobe,  and  is  formed  by  the  great  wing  of  the 
sphenoid,  the  squamous  and  petrous  portions  of  the  temporal  bone.  The 
points  to  be  noticed  in  this  fossa  are — 1.  '  The  sphenoidal  fissure '  between 
the  wings  of  the  sphenoid,  leads  to  the  orbit,  and  transmits  the  3rd,  the 
4th,  the  first  division  of  the  5th,  and  the  6th  nerves,  also  filaments  of 
the  sympathetic  nerve  and  the  ophthalmic  vein.  2.  The  '  foramen  rotun- 


98  HUMAN    OSTEOLOGY. 

dum '  gives  passage  to  the  superior  maxillary,  or  second  division  of  the  5th 
nerve.  3.  The  '  foramen  ovale '  gives  passage  to  the  inferior  maxillary, 
or  third  division  of  the  5th  nerve,  and  to  the  arteria  meningea  parva,  and 
sometimes  to  the  lesser  petrosal  nerve.  4.  The  '  foramen  spinosum '  gives 
passage  to  the  arteria  meningea  media  and  its  two  veins — the  main  trunk 
of  this  artery  grooves  the  squamous  part  of  the  temporal  and  the  anterior- 
inferior  angle  of  the  parietal  bone.  5.  The  '  foramen  lacerum  medium ' 
is  blocked  up,  in  the  recent  state,  by  fibro-cartilage;  the  Vidian  (great 
petrosal)  nerve  runs  through  this  cartilage.  The  internal  carotid  artery 
.also  passes  through  it.  6.  At  the  apex  of  the  petrous  portion  of  the  tem- 
poral bone  is  the  termination  of  the  '  carotid  canal '  through  which  the 
carotid  artery  enters  the  skull:  the  artery  then  winds  along  the  groove  on 
the  side  of  the  body  of  the  sphenoid.  7.  On  the  front  surface  of  the 
petrous  portion  of  the  temporal  bone  is  the  'hiatus  Fallopii/  which 
transmits  the  great  petrosal  nerve,  and  external  to  it  is  the  opening  of  the 
canal  for  the  lesser  petrosal  nerve.  Further  back,  on  the  same  surface, 
we  may  observe  the  eminence  for  the  superior  semicircular  canal.  8.  In 
the  centre  of  the  sphenoid  is  the  '  pituitary  fossa/  for  the  reception  of  the 
pituitary  body.  9.  The  '  posterior  clinoid  process/  like  the  anterior,  gives 
attachment  to  the '  tentorium  cerebelli/a  process  of  the  dura  mater  which 
supports  the  posterior  lobes  of  the  brain. 

Posterior  Fossa  of  the  Cranium. — The  posterior  fossa  is  the 
largest  and  deepest  of  the  cranial  fossae,  and  is  formed  by  the  occipital 
bone,  the  petrous  and  mastoid  parts  of  the  temporal  bone.  It  supports 
the  cerebellum.  Proceeding  from  before  backward,  we  observe,  in  the 
middle  line:  1.  The  'basilar  groove/  which  supports  the  medulla  obloii- 
gata  and  the  pons  Varolii.  2.  On  each  side  of  this  is  the  groove  for  the 
'inferior  petrosal  sinus.'  3.  Along  the  top  of  the  petrous  bone  is  the 
groove  for  the  '  superior  petrosal  sinus.'  4.  Both  these  sinuses  terminate 
in  the  great  '  lateral  sinus/  which  grooves  successively  the  occipital,  pos- 
terior-inferior angle  of  the  parietal,  mastoid  part  of  the  temporal,  and, 
last  of  all,  the  jugular  process  of  the  occipital  bone.  A  line  drawn  on  the 
outside  of  the  head,  from  the  occipital  protuberance  to  the  front  border 
of  the  mastoid  process,  corresponds  with  the  lateral  sinus.  On  the  pos- 
terior aspect  of  the  petrous  part  of  the  temporal  bone  is — 5.  The  '  meatus 
auditorius  internus/  for  the  facial  and  auditory  branches  of  the  7th  nerve 
and  the  little  auditory  artery.  6.  Some  distance  behind,  and  rather 
below  the  meatus,  is  the  '  aqueductus  vestibuli/  somewhat  concealed  by 


PLAI E  XX 


•jijjL Ant^palatine  canal 


.Pa.la.tvne  groove. 
.Posterior  palatine  canal. 

.Rid6e  or  palate  bone. 
.Accessory  palatine  canals . 

"•• BsstT-na-sal  gpirie. 

Ham  ular  process  . 

Sphenoid  a!\-Drocess  of  palate  Tsone. 

Pterygo-palattcie  ca.naL 

Scaphoid  fossa.. 

.Tor  am  en  ovale. 

Porame  cxlaceruraTmB^iviTn. . 

EoramerLSpmosuTtL 

Canal  for  Eustacliian  tiibe. 

Caroticl  ca,-r\a\. 

I 


men. 


Ibramen  for  Jaco'bsoris  • 

For  amen  lacerum  posters: 

Foramen  for  Arnold^  nerve 

Stylo-mastoidiroramen. 


oramen, 


li 

4 


•  vvTfW^^-v     ^ 

^•v.     *W  '"•  :^ 

^".WtS? 

^..External  Occipital  proper 

F) 


BASE    OF   THE    SKULL    AS   SEEN   FEOM    BELOW.  99 

an  overhanging  ridge  of  bone.     This  '  so-called  aqueduct '  transmits,  if 
anything,  a  small  vein  from  the  vestibule  of  the  ear. 

Behind  the  basilar  process  is — 7.  The  '  foramen  magnum/  which 
transmits  the  "spinal  cord  and  its  membranes,  the  vertebral  arteries,  and 
the  spinal  part  of  the  spinal  accessory  nerves.  8.  On  each  side  of  the 
foramen  magnum  are  the  'condyloid  foramina/  of  which  the  'anterior' 
transmits  the  hypoglossal  or  9th  nerve  (motor  nerve  of  the  tongue); 
the  '  posterior,'  a  vein  from  the  lateral  sinus  to  the  outside  of  the  skull. 
9.  The  '  mastoid  foramen '  also  transmits  a  vein  from  the  lateral  sinus  to 
the  outside  of  the  skull.  10.  Lastly,  the  '  foramen  lacerum  posterius '  trans- 
mits the  three  divisions  of  the  8th  nerve  and  also  the  blood  from  the 
lateral  sinus  into  the  internal  jugular  vein.  The  nerves  pass  through 
the  anterior  part  of  the  foramen,  which  is  separated  from  the  posterior 
by  a  bony  ridge. 


BASE  OF  THE  SKULL  AS  SEEN  FEOM  BELOW. 

(PLATES  XX.,  XXI.) 

The  base  of  the  skull  comprises  such  a  wide  area,  that  it  is  desirable  to 
draw  certain  limitary  lines.  If,  then,  a  line  be  drawn  from  the  first  in- 
cisor tooth  on  each  side,  backward  to  the  mastoid  process,  and  another 
transversely,  from  one  mastoid  process  to  the  other,  we  shall  describe  a 
triangle  within  which  are  contained  all  the  parts  usually  spoken  of  as  at 
the  base  of  the  skull. 

Arch  of  the  Palate*. — In  front  is  the  arch  of  the  'hard  palate, 
formed  by  the  superior  maxillary  and  palate  bones:  its  'middle'  and 
'  transverse '  sutures  cross  each  other  at  right  angles.  A  pin  introduced 
at  the  point  of  crossing  would  touch  five  bones,  the  5th  being  the  vomer. 
Generally  speaking,  when  the  palate  presents  a  fine  arch,  free  from  con- 
traction in  any  direction,  the  voice  is  clear  and  sonorous.  The  best 
singers  have  always  well-formed  palates.  Its  surface  is  rugged  for  the 
lodgment  of  the  palatine  glands,  and  it  is  riddled  with  minute  holes  for 
the  passage  of  blood-vessels.  Behind  the  incisor  teeth  is  the  '  anterior 
palatine  canal ' ;  a  single  orifice  below,  but  double  above,  so  as  to  open 
separately  into  each  nostril.  It  transmits  the  anterior  palatine  vessels 
and  naso-palatine  nerves  (see  also  p.  73).  Near  the  last  molar  tooth  is 


100  HUMAN    OSTEOLOGY. 

the  orifice  of  the  'posterior  palatine  canal/  formed  conjointly  by  the 
palate  and  superior  maxillary  bones:  and  from  this  we  trace  forward  the 
'  palatine  groove '  for  the  lodgment  of  the  descending  palatine  vessels  and 
the  large  palatine  nerve.  Lastly,  there  is  the  '  ridge '  on  the  palate  bone 
for  the  attachment  of  the  '  tensor  palati/  and  the  '  posterior  nasal  spine/ 
to  which  is  attached  the  '  azygos  uvulae.' 

Posterior  Openings  of  Nose. — Behind  the  palate  are  the  poste- 
rior openings  of  the  nasal  fossae,  separated  by  the  sharp  edge  of  the  vomer. 
Each  opening  is  somewhat  oval,  about  one  inch  in  the  long  diameter  and 
half  an  inch  in  the  transverse.  We  should  remember  this  in  plugging 
the  nostril.  It  is  bounded,  above,  by  the  body  of  the  sphenoid  and  the 
sphenoidal  process  of  the  palate  bone;  below  by  the  horizontal  plate  of  the 
palate;  outside,  by  the  internal  pterygoid  plate  of  the  sphenoid;  and 
inside,  by  the  vomer.  On  the  roof  of  each  are  the  expanded  '  wings'  of 
the  vomer,  which  receive  between  them  the  '  rostrum '  of  the  sphenoid; 
and  also  the  '  ptery go-palatine  canal.'  This,  as  its  name  implies,  is 
formed  conjointly  by  the  pterygoid  plate  of  the  sphenoid  and  the  sphe- 
noidal process  of  the  palate  bone.  It  transmits  a  branch  of  the  internal 
maxillary  artery,  and  a  pharyngeal  nerve  from  the  spheno-palatine 
ganglion  to  the  top  of  the  pharynx. 

Pterygoid  Region. — On  each  side  of  the  nasal  openings  are  the 
'  pterygoid  processes '  of  the  sphenoid.  These  pterygoid  processes  bound 
the  posterior  openings  of  the  nose:  act  as  buttresses  to  support  the  upper 
jaw-bones  behind;  and  serve  for  the  origin  of  the  powerful  pterygoid 
muscles  which  grind  the  food.  From  the  pterygoid  fossa,  or,  more 
strictly,  from  the  inner  surface  of  the  external  pterygoid  plate  and  the 
back  of  the  tuberosity  of  the  palate  bone  which*  fits  into  the  gap  between 
the  pterygoid  processes,  arises  the  '  pterygoideus  internus ' ;  while  the 
outer  surface  of  the  same  plate  and  the  adjacent  outer  aspect  of  the  tu- 
berosity of  the  palate  bone  give  origin  to  the  'pterygoideus  externus.' 
At  the  base  of  the  internal  plate  is  the  scaphoid  fossa,  for  the  origin  of 
the  '  tensor  palati ' ;  and  at  the  apex  is  a  pulley,  termed  the  '  hamular  pro- 
cess/ around  which  the  tendon  of  this  muscle  plays.  Besides  this,  the 
hamular  process  gives  origin  to  part  of  the  '  superior  constrictor '  of  the 
pharynx.  Immediately  above  the  '  scaphoid  fossa '  is  the  posterior  orifice 
of  the  Vidian  canal. 

Proceeding  backward  from  the  base  of  the  pterygoid  processes,  we 
come  next  upon  the  great  foramina  at  the  base  of  the  skull,  most  of 


PLATE  XXI. 


BASE*  OF  THE  SKULL  AS  SEEN  FROM  BELOW. 


101 


which  have  already  been  seen  in  the  examination  of  the  base  from  above. 
In  the  great  wing  of  the  sphenoid  there  is  the '  foramen  ovale.'  The  fora- 
men rotundum  cannot  be  seen  at  the  inferior  part  of  the  base  of  the 
skull:  look  for  it  at  the  back  of  the  orbit.  Behind  the  foramen  ovale  is 
the  '  foramen  spinosum ' ;  and  still  farther  back  is  the  apex  of  the  wing, 
termed  the  '  spinous  process/  which  is  wedged  between  the  squamous  and 
petrous  bones,  and  gives  attachment  to  the  internal  lateral  ligament  of 
the  lower  jaw  and  the  '  laxator  tympani.'  From  the  spinous  process  we 
trace  outward  the  '  glenoid  fissure/  which  runs  across  the  glenoid  cavity 
of  the  temporal  bone.  Between  the  sphenoid  and  petrous  bones  is  the 
canal  for  the  k  Eustachian  tube '  (running  ia  the  same  line  as  the  Glaserian 
fissure),  which  is  completed  in  the  recent  state  by  fibro-cartilage. 

Petrous    Region. — The  petrous  portion  of  the  temporal  bone   is 
wedged  in  between  the  sphenoid  and  the  basilar  process  of  the  occipital. 


FIG.  21.— Diagram  of  the  Relative  Positions  of  the  more  important  parts  at  the  Base  of  the  SkuIL 
The  dotted  arrow  shows  that  the  mastoid  process,  the  stylo-mastoid  foramen,  the  styloid  process,  and 
the  spinous  process  of  the  sphenoid  (represented  by  stars),  and  the  Eustachian  tube  are  pretty  nearly 
to  a  line. 


Outside  the  arrow  are — 

1.  Scaphoid  fossa. 

2.  Foramen  ovale. 

8.  Foramen  spinosum. 

4.  Spinous  process. 

5.  Fissura  Glaseri. 

6.  Meat  us  auditorius  externus. 


Inside  the  arrow  are — 

7.  Pterygo-palatine  canal. 

8.  Foramen  lacerum  medium, 

9.  Carotid  canal. 

10.  Foramen  jugulare. 

11.  Notch  for  8th  pair  of  nerves. 

12.  Anterior  condyloid  foramen. 


Observe  that  the  apex  of  the  wedge  is  cut  short,  so  that  an  irregular  open- 
ing remains  between  the  three  bones,  termed  the  'foramen  lacerum 
medium.'  In  the  recent  skull  this  space  is  filled  with  cartilage,  through 


102  HUMAN    OSTEOLOGY. 

which  pass  the  internal  carotid  artery,  surrounded  with  filaments  of  the 
sympathetic  nerve,  and  the  Vidian  nerve.  The  apex  of  the  petrous  bone 
gives  origin  to  the  '  tensor  tympani'  and  '  levator  palati.'  In  the  middle 
of  the  petrous  bone  is  the  wide  orifice  of  the  carotid  canal  which  trans- 
mits the  carotid  artery.  Trace  this  canal,  and  you  will  find  that  it  does 
not  enter  the  cranial  cavity  directly,  but  that  it  ascends  for  a  short  dis- 
tance, and  then  runs  horizontally  forward  and  inward  through  the  petrous 
bone,  till  it  opens  at  the  apex  into  the  foramen  lacerum.  Thus  the 
carotid  artery  makes  two  curves,  like  the  letter  S,  before  it  enters  the 
cranium — the  first  curve  in  the  bony  canal,  and  the  second  through  the 
cartilage  which  fills  up  the  foramen  lacerum.  This  disposition  of  the 
great  arteries  at  the  base  checks  the  force  of  the  blood  on  its  passage  to 
the  brain. 

Behind  the  carotid  canal  is  the  '  foramen  lacerum  posterius/  or  '  fora- 
men jugulare/  another  opening  left  between  the  petrous  and  occipital 
bones.  The  size  and  shape  of  it  are  subject  to  great  variety.  The  right 
jugular  foramen,  is  usually  larger  than  the  left,  but  it  is  generally  di- 
vided by  a  projecting  tongue  of  bone  into  an  anterior  part,  which  trans- 
mits the  eighth  pair  of  nerves,  and  a  posterior,  which  is  by  far  the  larger, 
for  the  passage  of  the  blood  from  the  lateral  sinus  into  the  commencement 
of  the  internal  jugular  vein.  The  posterior  meningeal  arteries  (from  the 
occipital  and  ascending  pharyngeal  branches  of  the  external  carotid)  also 
enter  the  cranium  through  this  aperture. 

Outside  the  foramen  lacerum  posterius  is  the  '  styloid  process/  pro- 
jecting, more  or  less,  beyond  the  *  vaginal  process '  at  its  root.  Behind 
this  is  the  '  stylo-mastoid  foramen/  through  which  the  facial  nerve 
emerges  from,  and  the  stylo-mastoid  artery  enters,  the  skull.  Still  farther 
back  is  the  mastoid  process,  and  the  digastric  fossa  for  the  origin  of  the 
digastric  muscle.  Internal  to  this  fossa  may  generally  be  seen  a  groove 
for  the  occipital  artery. 

Basilar  Process. — The  basilar  process  of  the  occipital  bone  projects 
into  the  base  of  the  skull,  and  joins  the  body  of  the  sphenoid:  here  it 
forms  the  roof  of  the  pharynx.  This  relation  is  of  practical  importance, 
because  the  basilar  process  is  within  reach  of  the  finger  introduced  into 
the  mouth,  and  can  be  explored  so  as  to  determine  how  far  a  polypus 
may  be  connected  with  it.  It  affords  insertion  to  the  '  rectus  capitis  an- 
ticus  major'  and  '  minor/  and  (by  means  of  a  little  tubercle)  to  the  aponeu- 
rosis  of  the  pharynx.  Behind  the  basilar  process  is  the  '  foramen  mag- 


TEMPORAL    AND    ZYGOMATIC    FOSSAE.  103 

num.'  On  each  side  of  this  are  the  'condyles'  of  the  occiput,  with  the 
'  anterior '  and  '  posterior  condyloid '  foramina;  and  on  the  outside  of  each 
condyle  is  the  jugular  eminence,  which  gives  insertion  to  the  '  rectus  ca- 
pitis  lateralis.' 

Occipital  Foramen. — In  a  well-formed  European  skull,  the  plane  of 
the  occipital  foramen  is  horizontal  when  the  body  is  erect,  and  its  anterior 
extremity  is  about  half  way  between  the  tuberosity  of  the  occipital  bone 
and  the  incisors  of  the  upper  jaw.  This  central  position  of  the  occipital 
foramen  and  the  condyles  is  one  of  the  great  peculiarities  of  man,  who 
stands  erect.  His  head,  therefore,  is  almost  equally  balanced  on  the  top 
of  the  spine.  In  monkeys,  who  hold  a  middle  rank  between  man  and 
quadrupeds,  the  foramen  magnum  is  placed  farther  back:  in  the  orang- 
outan,  it  is  about  twice  as  far  from  the  foramina  incisiva  as  from  the  back 
of  the  head.  Consequently,  although  monkeys  can  stand  erect  for  a 
time,  they  cannot  do  so  long.  In  quadrupeds,  again,  the  foramen  mag- 
num is  still  nearer  to  the  back  of  the  head,  and  its  plane  forms  a  consider- 
able angle  with  the  horizon.  The  weight  of  the  head  in  quadrupeds  is 
sustained,  not  only  by  the  spine,  but  by  an  elastic  ligament  of  great 
strength  (ligamentum  nuchae),  which  arises  from  the  lofty  spines  of  the 
dorsal  vertebrae,  and  is  fixed  to  the  crest  of  the  occiput. 


TEMPORAL,  ZYGOMATIC,  AND  SPHENO-MAXILLARY 
FOSSAE. 

The  temporal  fossa  (see  page  94)  leads  into  the  zygomatic  fossa,  the 
boundary  between  them  being  the  crest  of  the  sphenoid  bone.  » 

Zygomatic  Fossa. — The  '  zygomatic  fossa '  is  bounded  externally 
by  the  zygomatic  arch,  which  serves  as  a  strong  buttress  to  support  the 
bones  of  the  face,  and  gives  origin  to  the  powerful  '  masseter '  muscle 
which  closes  the  mouth.  In  front  of  the  fossa  there  is  the  back  part  of 
the  superior  maxilla,  and  at  the  bottom  of  it,  the  outer  pterygoid  plate 
of  the  sphenoid,  which  gives  origin  to  the  external  pterygoid  muscle. 
At  the  deepest  part  of  the  fossa  are  two  wide  fissures  at  right  angles  to 
each  other:  one,  nearly  horizontal,  leads  into  the  orbit,  and  is  called  the 
'  spheno-maxillary  fissure,'  through  which  the  infra-orbital  nerve  and 


104  HUMAN    OSTEOLOGY. 

artery  enter  the  floor  of  the  orbit  to  reach  their  canal  in  the  superior 
maxillary  bone. 

Spheno-maxillary  Fossa.  —  The  other  fissure,  nearly  vertical,  leads 
to  the  '  spheno-maxillary  fossa/  in  which  the  third  part  of  the  internal 
maxillary  artery  breaks  up  into  terminal  branches.  This  fossa  is  bounded 
in  front  by  the  back  of  the  superior  maxilla;  behind,  by  a  smooth  surface 
at  the  base  of  the  pterygoid  process;  internally,  it  is  separated  from  the 
nasal  fossae  by  the  perpendicular  plate  of  the  palate  bone. 

There  are  five  openings  into  the  spheno-maxillary  fossa  (see  Plate 
XXII.),  as  follows:— 

FIVE  OPENINGS  INTO   SPHENO-MAXILLARY  FOSSA. 

f  transmits  into  f  Internal    or    nasal    branches    of« 
1.   Spheno  -  palatine  J      ,  ,  -.1       spheno-palatine  ganglion. 


foramen  fossa  I  -^asa^  or  sPnenc~palatine  branch  of 

I      internal  maxillary  artery. 

2.  Posterior-palatine  j  transmits    to  j  Descending   palatine    artery  and 

canal  (     the  palate      (      large  palatine  nerve. 

3.  Foramen     rotun-  (  (  Superior  maxillary  nerve,  or  sec. 

]  transmits          1 
dum  (      ond  division  of  fifth  pair. 

4.  Vidian  canal  transmits  Vidian  artery  and  nerve. 

f  Pterygo-palatine    branch    of    in- 

5.  Pterygo  -  palatine  j  ternal    maxillary    artery,    and 

canal  (     '  pharyngeal  nerve  from  Meckel's 

I      ganglion. 


THE   ORBITS. 

The  orbits,  or  sockets  for  the  eyes,  are  like  crypts  excavated  beneath 
the  cranium.  (Plate  XVIII.)  To  use  the  words  of  Sir  Charles  Bell, 
'  these  under  arches  are  groined  ; '  that  is  to  say,  they  are  provided  with 
strong  ribs  of  bone,  so  that  there  is  no  need  of  thick  bone  in  the  inter- 
stices of  the  groinings.  The  plate  between  the  eye  and  the  brain  is  as  thin 
as  parchment:  but  look  how  strong  is  the  arch  forming  the  orbital  mar- 
gin, and  what  a  strong  ridge  of  bone  runs  up  from  the  zygoma,  like  a 
buttress  to  support  the  side  of  the  arch.  When  the  eye  is  threatened  and 


PL.VTE  XXII. 


lachrymal  tone         Groove  fomasal<l"ucb; 


-AnlfethTno'idal  foramen,. 
PostTetVimoidal  foramen. 


Body  o?  5"shen6i3  bone,     i 

!        '. 

Palate  tone,  '; 


io    ilatine  -for«mer\ 
at 

\\Wy  fossa..  •  •• 


Ivtax'tlUr/  process  of  inf 


Uniform  process  *P  "Et>imoia  tone 


of  the  "Bone?  a-nd.ForaTrLi.ua- 
on  LHfcTnner  wall  oF  the  Orbit,  the  five  ope  nm^s  into  the 
3pheno4mudlkry  fossa  .the  AntruTv  and  bones  cuntra-cti-ncj  its  orifice. 


THE     CEBITS.  105 

somewhat  retracted  in  its  socket,  the  margin  of  the  orbit  is  more  than 
strong  enough  to  protect  it  from  the  effects  of  violence. 

Each  orbit  is  pyramidal,  with  the  apex  behind.  Their  axes,  if  pro- 
longed, would  pass  through  the  optic  foramina,  and  meet  behind  the 
pituitary  fossa  of  the  sphenoid.  This  divergence  gives  a  greater  range  of 
vision.  The  anterior  opening  of  the  orbit  is  quadrilateral  and  consists 
of  an  upper,  a  lower,  an  inner  and  an  outer  margin.  In  the  higher  types 
of  man  these  openings  are  more  rounded. 

Upper  Wall  of  Orbit. — The  upper  wall  of  the  orbit  is  slightly 
arched,  and  formed  by  the  frontal  bone  and  lesser  wing  of  the  sphenoid. 
On  this  wall  are — 1,  the  optic  foramen;  2,  the  fossa  beneath  the  external 
angular  process  for  the  lachrymal  gland;  3,  the  little  depression  for  the 
pulley  of  the  '  superior  oblique '  muscle;  4,  the  supra-orbital  foramen  or 
notch,  situate^,  at  the  junction  of  the  inner  with  the  middle  third  of  the 
orbital  margin. 

Lower  Wall  or  Floor  of  Orbit. — The  lower  wall  of  the  orbit 
slopes  downward  and  outward,  and  is  formed  by  the  orbital  plate  of  the 
superior  maxilla,  by  part  of  the  malar  bone,  and  behind  by  the  orbital 
plate  of  the  palate  bone.  On  this  wall  is  the  groove  for  the  infra-orbital 
nerve. 

Inner  Wall  of  Orbit.— The  inner  wall  (Plate  XXII.)  is  formed  by 
the  nasal  process  of  the  superior  maxilla,  by  the  lachrymal,  the  os  planum 
of  the  ethmoid,  and  the  side  of  the  body  of  the  sphenoid  bone.  Here  we 
observe  the  groove  for  the  nasal  duct,  formed  conjointly  by  the  nasal 
process  of  the  superior  maxilla,  the  lachrymal,  and  the  inferior  spongy 
bone.  Its  direction  is  downward,  backward,  and  a  little  outward,  and  it 
leads  into  the  inferior  meatus  of  the  nose.  Besides  this,  there  are  the 
1  anterior  and  posterior  ethmoidal  foramina.' 

Outer  Wall  of  Orbit.— The  outer  wall  of  the  orbit  is  formed  by 
the  malar  bone  and  the  orbital  plate  of  the  great  wing  of  the  sphenoid. 
Here  there  are  one  or  two  small  foramina  (malar  canals),  which  transmit 
small  nerves  from  the  orbit  to  the  skin  of  the  cheek  and  temple.  (See  p. 
77.)  The  outer  wall  of  the  orbit  recedes  more  than  the  other  parts  of 
its  circumference,  giving  so  great  a  range  of  vision  externally,  that  by 
rotating  the  head  on  each  side  of  the  spine,  we  can  see  all  round. 

Bones  Composing  Orbit. — Look  into  the  orbit  and  examine  two 
four-sided  plates,  one  on  the  inner  side  belonging  to  the  ethmoid,  and  one 
on  the  outer  belonging  to  the  great  wing  of  the  sphenoid.  The  four-sided 


106  HUMAN    OSTEOLOGY. 

plate  of  the  ethmoid  articulates  above  with  the  frontal;  below  with  the 
superior  maxillary  bone,  in  front  with  the  lachrymal  and  behind  with 
the  sphenoid.  Besides  these  the  orbital  process  of  the  palate  bone  here 
comes  up  between  the  sphenoid  and  superior  maxilla  (articulating  with 
both  of  them)  and  joins  the  posterior  inferior  angle  of  this  plate.  The 
four-sided  plate  of  the  sphenoid  articulates  likewise  with  the  frontal  bone 
above,  which  arches  over  from  the  top  of  the  aforesaid  plate  of  the  eth- 
moid; below,  its  edge  is  separated  from  the  superior  maxillary  bone  by 
the  spheno- maxillary  fissure;  in  front,  it  articulates  with  the  malar  bone, 
and  behind,  its  edge  is  separated  from  the  rest  of  the  sphenoid  by  the 
sphenoidal  fissure.  These  articulations  should  be  traced  on  the  bones  and 
thoroughly  mastered.  Thus,  seven  bones  enter  into  the  composition  of 
each  orbit:  namely — the  frontal,  ethmoid,  and  sphenoid,  the  superior 
maxilla,  the  malar,  the  lachrymal,  and  the  palate;  but  there  are  only 
eleven  bones  in  the  two  orbits,  since  the  first  three  bones  are  common  to 
both. 

Sphenoidal  and  Spheno-maxillary  Fissures. — At  the  back  of 
the  orbit  are  two  wide  fissures  for  the  admission  of  blood-vessels  and 
nerves.  The  upper  one  is  the  '  sphenoidal  fissure/  formed  between  the 
greater  and  lesser  wings  of  the  sphenoid  bone.  It  leads  into  the  cranium, 
and  transmits  the  third  and  fourth  nerves,  the  ophthalmic  branch  of  the 
fifth,  the  sixth  nerve,  some  filaments  of  the  sympathetic  nerve,  and  the 
ophthalmic  vein.  The  lower  one,  the  '  spheno-maxillary  fissure' 
leads  into  the  zygomatic  fossa.  The  borders  of  this  fissure  are  formed 
internally  by  the  superior  maxillary  and  palate  bones,  externally  by 
the  sphenoid.  It  is  completed  in  front  by  the  malar.63  Through  this 
fissure  the  infra-orbital  artery  and  the  superior  maxillary  nerve  enter  the 
groove  along  the  floor  of  the  orbit. 

There  are  some  points  of  practical  interest  about  these  two  fissures. 
1.  In  blows  on  the  temple,  blood  is  apt  to  make  its  way  through  the 
splieno-maxillary  fissure  into  the  orbit,  and  produce  ecchymosis  under  the 
conjunctiva.  2.  In  the  operation  for  the  removal  of  the  superior  max- 
illary bone,  we  saw  through  the  orbital  wall  into  the  fissure,  so  that  it  is 
requisite  to  know  its  precise  position.  Concerning  the  sphenoidal  fissure, 
we  should  know  that:  1.  In  fracture  through  the  base  of  the  skull,  involv- 
ing this  fissure,  the  effused  blood  may  make  its  way  into  the  orbit  and 

63  Except  in  cases  where  the  sphenoid  and  superior  maxillary  come  into  contact, 
and  exclude  the  malar.  (See  note,  37.) 


PLATE  XXIII. 


ITasal  spine  of- 
Fronts  bone 

CrestoF  Nasal  bone 


Perpendicular  plate  of 
Ethmoid  bone 


Crest  oE  su  p^Maxillary  "bone 


{SpTneno'tcl  bone 


Crest  oF  Palate  tone. 


View  of  the  Septum,  of  tVeTSIose 


Prdbe.passecJ  from  Frontal  pm  us  into  Middle  meabus 

Middle  £>pon^y  bone. 
Superior  Meatus.. 
Superior  Sf>on£y  bone 


Ptery^o  palatine  canal.. 
Spheno -palatine  Foramen 

Msaaie-meatus 

Inferior  meatu  s..- - 


bone, 
m'bc 
.  .Or i  Flee  oF  Anbrum 

^Sponbybone. 


View  of  the  three' Meabus*  oF  tY\e~Noae. 


NASAL    FOSSJE.  107 

produce  ecchymosis  of  the  conjunctiva.  2.  A  sharp  instrument  might 
penetrate  through  this  fissure  into  the  brain.  Surgery  has  such  cases  on 
record.  Here  is  one.  Henry  II.  of  France,  one  of  the  last  princes  of 
the  House  of  Valois,  was  mortally  wounded  by  Montgomery,  captain  of 
the  body  guard,  in  a  tournament  held  in  1559,  on  the  occasion  of  the 
marriage  of  Philip  II.  with  Elizabeth  of  France.  A  splinter  from  a  lance 
entered  through  the  sphenoidal  fissure,  stuck  fast  and  could  not  be  ex- 
tracted. The  king  died  on  the  eleventh  day. 


NASAL    FOSSAE. 

(PLATE  XXIII.) 

These  cavities  open  widely  in  front,  and  admit  the  air  through  the 
nostrils,  and  behind  into  the  top  of  the  pharynx.  To  study  them  prop- 
erly it  is  indispensable  to  have  a  skull  divided  longitudinally  on  one 
side  of  the  septum,  so  that  we  can  examine  the  roof,  the  floor,  the  outer 
and  inner  surfaces  of  the  cavities. 

Boundaries  of  Nasal  Fossae. — The  '  roof '  of  the  nasal  fossae  is 
formed  by  the  nasal  bones,  by  the  nasal  spine  of  the  frontal,  the  cribri- 
form plate  of  the  ethmoid,  and  the  body  of  the  sphenoid.  It  does 
not  form  a  horizontal  plane  from  before  backward.  It  is  only  the  cribri- 
form plate  which  is  horizontal;  from  this,  the  roof  slopes  forward  toward 
the  nose,  and  backward  toward  the  pharynx:  therefore  the  vertical  depth 
is  much  greater  in  the  middle  than  elsewhere.  Notice  the  greater  thin- 
ness of  the  cribriform  plate,  and  how  easily  an  instrument  might  be 
thrust  through  this  part  of  the  roof  into  the  brain.  Herodotus,64  in  his 
excellent  description  of  the  process  of  embalming  the  dead,  as  practised 
by  the  ancient  Egyptians,  mentions  that  they  drew  out  the  brain  through 
the  nostrils  with  an  iron  hook,  and  filled  up  the  void  by  injecting  drugs. 
In  the  fine  series  of  ancient  Egyptian  skulls,  brought  from  the  great 
necropolis  of  Thebes  by  Professor  Flower,  and  now  in  the  Museum  of  the 
Royal  College  of  Surgeons  (Nor.  Hum.  Ost.,  Nos.  584  to  593),  it  may  be 
seen  that  in  every  one  of  them  the  cribriform  plate  is  broken  away,  and 
the  bones  of  the  nasal  fossae  more  or  less  damaged;  an  interesting  proof 
of  the  veracity  of  the  ancient  historian. 

84  '  Euterpe, '  chap.  86,  87,  88. 


108  HUMAN    OSTEOLOGY. 

The  '  floor '  is  nearly  horizontal,  and  is  formed  by  the  palate  plates 
of  the  superior  maxillary  and  palate  bones.  In  the  dry  bones  can  be 
seen,  on  each  side  of  the  septum,  the  orifice  of  the  '  anterior  palatine 
canal'  (p.  74). 

IVJeatus  of  the  Nose. — The  outer  wall  of  the  nasal  fossae  is  made 
irregular  by  the  '  meatus '  or  passages  in  the  nose,  and  the  numerous 
openings  leading  to  the  air-cells,  in  the  neighboring  bones.  It  is  formed 
by  the  ethmoid  (including  its  two  turbinated  bones),  the  nasal,  the  su- 
perior maxillary,  the  lachrymal,  the  inferior  turbinated,  the  palate,  and 
the  internal  pterygoid  plate  of  the  sphenoid.  It  is  important  to  observe 
the  position  of  the  turbinated  bones  and  the  three  *  meatus '  or  passages 
of  the  nose.  (Plates  XXIII.  and  XXIV.) 

Superior  Meatus. — Beneath  the  superior  turbinated  bone  lies  the 
'  superior  meatus/  into  which  open  the  posterior  ethmoidal  cells  and 
the  sphenoidal  cells.  At  the  back  part  of  this  meatus  is  the  spheno-pala- 
tine  foramen,  which  leads  into  the  spheno-maxillary  fossa. 

Middle  Meatus. — Below  the  middle  turbinated  bone  is  the  '  middle 
meatus/  Into  this  open — 1,  toward  the  front,  the  frontal  sinus  (or  cell), 
along  a  passage  termed  the  '  infundibulum ';  2,  the  anterior  ethmoidal 
cells  (distinct  from,  the  posterior);  3,  the  antrum  or  maxillary  sinus.  The 
orifice  of  the  antrum  is  large  and  irregular  in  the  dry  bones;  but  in  the 
recent  state  it  is  so  narrowed  by  mucous  membrane  that  it  will  just  admit 
a  crow-quill. 

Inferior  Meatus. — Below  the  inferior  turbinated  bone  is  the  'inferior 
meatus/  No  air-cells  open  into  this  meatus:  there  is  only  the  termina- 
tion of  the  nasal  duct  or  channel  which  conveys  the  tears  into  the  nose: 
this  cannot  be  seen  without  removing  part  of  the  turbinated  bone. 

"  The  openings  into  the  several  '  meatus  *  of  the  nose  may  be  thus  tabu- 
lated:— 

( The  sphenoidal  cells. 
Into  the  SUPERIOR  MEATUS         .     open  ^  m 

(  The  posterior  ethmoidal  cells. 

fThe  anterior  ethmoidal  cells. 
Into  the  MIDDLE         .        .        .     open  <!  The  frontal  cells. 

[The  antrum. 
Into  the  INFERIOR       .        .        .     opens   The  nasal  duct. 

The  two  upper  turbinated  bones  (belonging  to  the  ethmoid)  are  deli- 
cately channelled  for  the  lodgment  of  the  olfactory  nerves.  The  lower 


PLATE  XXIV. 


Section  showing  ,the  Mieatus' oftHeNose. 


Nasal  bone. 

NapaL  process  of  the  upper  Jaw. 

NassQ  spine  oF  tine  Frontal  bone] 
.'.-.Perpendicular plate  of  Ethrnoi^bone. 


Section,  showing  iheTtfasalarck . 


GENERAL  OBSERVATIONS  ON  THE  SKULL.         109 

or  third  turbinated  bone  has  nothing  to  do  with  the  sense  of  smell,  and 
is  coarser  in  its  texture.  It  is  traversed  by  several  canals  and  grooves, 
which  run  from  before  backward,  and  in  the  recent  state  contain  large 
veins.  The  turbinated  bones  do  not  extend  throughout  the  whole  length 
of  the  outer  wall.  All  the  surface  in  front  of  a  perpendicular  line  let 
fall  from  the  nasal  spine  of  the  frontal  bone  is  smooth,  as  is  also  all  the 
surface  behind  a  perpendicular  line  from  the  spheno-palatine  foramen. 

Bones  forming  Septum  of  Nose. — The  bony  septum  of  the  nose, 
one  of  the  principal  supports  of  the  nasal  arch  (Plate  XXIII.),  is  formed 
chiefly  by  the  perpendicular  plate  of  the  ethmoid  and  the  vomer.  (Plate 
XXIV.  Fig.  2.)  The  formation  of  the  septum  is  assisted  by  the  nasal 
spine  of  the  frontal,  the  crests  of  the  nasal,  superior  maxillary,  and 
palate  bones;  also  by  the  rostrum  or  crest  of  the  sphenoid,  making  ten 
bones  in  all.  The  triangular  interval  left  in  the  septum  in  the  dry  skull 
is  filled  up  in  the  perfect  one  by  the  middle  cartilage  of  the  nose,  which 
fits  into  a  fissure  in  the  bone. 

The  posterior  openings  of  the  nasal  fossae  have  been  already  described 
in  the  '  base  of  the  skull '  (p.  107).  The  anterior  opening  is  heart-shaped, 
with  the  broad  part  below.  It  is  bounded  on  either  side  by  the  nasal 
bone,  and  by  the  nasal  process  of  the  superior  maxilla;  below  it  is 
bounded  by  the  palatine  process  of  this  bone,  which  terminates  in  front 
by  a  sharp  projection,  termed  the  '  anterior  nasal  spine/  the  prominence 
of  which  is  a  marked  feature  in  the  higher  races  of  mankind.  It  is 
very  diminutive  in  some  of  the  lower  races,  and  absent  in  monkeys. 

GENERAL  OBSERVATIONS  ON  THE  SKULL. 

Skull  a  Lever  of  the  First  Order.— The  entire  skull  represents 
a  lever  of  the  first  order.     The  fulcrum  or  point  of  sup- 
port F  (see  Fig.  22)  is  at  the  occipito-atlanteid  articu- 
lation; the  resistance  is  the  weight  of  the  head  W;  the 
power  P  is  the  mass  of  muscle  attached  to  the  occiput. 
The  skull  is  nearly  balanced  on  the  spine,  and  the  mus- 
cles moving  it  have  but  small  leverage.    Contrast  this,  how- 
ever, with  that  of  the  elephant  (see  p.  38),  the  massive          Flo-  22. 
appendages  of  whose  head  have  proportionally  strong  muscles  and  liga- 
ments for  their  movements  and  support. 

Three  Layers  or  Tables  of  the  Skull. — The  cranial  bones 
consist  of  three  layers — an  outer,  an  inner,  and  an  intermediate  'diploe.' 


110  HUMAN   OSTEOLOGY. 

The  outer  is  formed  of  compact  and  tough  bone;  the  inner  is  harder,  but 
more  brittle  (hence  called  '  tabula  vitrea ') ;  while  the  diploe  is  softer  and 
spongy,  and  diminishes  the  effects  of  shocks.  Altogether,  then,  this  struc- 
ture may  be  coarsely  compared  to  a  case  composed  of  wood  outside,  por- 
celain inside,  and  soft  leather  between  the  two. 

The  different  structure  of  these  three  layers  or  *  tables '  of  the  skull 
is  interesting  practically.  In  blows  on  the  head,  the  inner  table,  in  con- 
sequence of  its  great  brittleness,  is  likely  to  be  broken  more  extensively 
than  the  outer.  Cases  indeed  have  occurred,  where  the  inner  table  has 
been  broken  without  any  fracture  of  the  outer.  In  sabre  cuts  penetrating 
the  skull-cap  as  deep  as  the  inner  table,  although  the  cut  through  the 
outer  table  may  be  only  a  simple  incision  without  any  depression,  yet  the 
inner  table  will  be  broken  almost  always  to  a  greater  extent  than  the 
outer:  indeed,  it  may  be  separated  from  it,  and  driven  into  the  mem- 
branes if  not  into  the  substance  of  the  brain.65  Hence  the  necessity  of 
examining  these  cases  very  carefully,  to  ascertain  if  there  be  any  parts 
of  the  inner  table  depressed,  and  to  remove  them.  Another  reason  why 
the  inner  table  is  often  more  extensively  splintered  than  the  outer  is, 
that  it  is  the  last  table  reached  by  the  force  which  inflicts  the  damage. 
The  aperture  of  exit  of  a  bullet  is  larger  than  that  of  its  entry.86  (See 
injuries  and  diseases  of  bone,  No.  2901  E.) 

Locking  of  the  Bones. — The  bones  are  mechanically  locked  to- 
gether by  the  sutures;  and  in  the  recent  state  there  is  a  thin  layer  of 
animal  matter  between  their  edges,  which  dimin- 
ishes the  effects  of  blows.  Whoever  knows  the 
strength  of  an  egg-shell,  can  understand  what 
hard  blows  the  cranium  will  bear.  Most  of  the 
bones  mutually  support  each  other,  by  having 
their  edges  bevelled  alternately  on  opposite 
sides,  as  in  the  frontal  suture;  or  by  one  over- 
lapping the  other,  as  in  the  squamous  suture, 

where  the  temporal  prevents  the  '  starting '  of  the  parietal  bone  (see 
Fig.  23).  The  effect  of  this  is,  that  no  single  bone  can  be  taken  out 
of  the  cranium  without  separating  the  whole  fabric.  (Nor.  Hum.  Ost., 
No.  175.)  When  we  wish  to  separate  the  bones,  we  do  so,  not  by  force 
from  without,  but  by  force  from  within  the  skull;  that  is,  by  introducing 

65  Guthrie,  '  Commentaries,'  Lecture  xviii. 
06  See  Erichsen,  '  Science  and  Art  of  Surgery.' 


GENERAL    OBSERVATIONS   ON   THE   SKULL.  Ill 

peas,  which,  when  moistened  with  water,  swell,  and  by  pressing  equally 
in  all  directions  disjoint  the  bones. 

Groins  along  the  Sinuses. — Notice  how  the  interior  of  the  dome 
is  strengthened  by  '  ribs'  or  '  groins'  of  bone,  which  run  in  the  line  of  the 
principal  sinuses.  One  rib  extends  from  the  centre  of  the  frontal  bone 
to  the  foramen  magnum,  and  spans  from  before  backward  the  whole  arch 
of  the  cranium.  Another  crosses  transversely  the  back  part  of  the  occipi- 
tal bone;  the  point  of  intersection  of  these  two  ribs  being  at  the  occipital 
protuberance,  which  is  the  thickest  and  strongest  part  of  the  skull. 

Buttresses  of  the  Skull. — Like  all  other  arches,  the  cranium 
transmits  shocks  toward  its  buttresses;  these  are  firmly  wedged  into  the 
base,  and  all  meet  at  the  centre,  that  is,  at  the  body  of  the  sphenoid. 
The  frontal  part  of  the  arch  is  supported  by  the  wings  of  the  sphenoid 
and  the  malar  bones,  the  parietal  part  by  the  temporal  bones,  and  the 
occipital  part  supports  itself  by  running,  wedge-like,  into  the  base,  and 
abutting  on  the  sphenoid.  A  knowledge  of  the  buttresses  which  support 
the  respective  parts  of  the  skull-cap  affords  an  explanation  of  the  direc- 
tion which  fractures  generally  take  along  the  base  of  the  skull,  according 
as  the  injury  has  been  received  on  the  frontal,  the  parietal,  or  the  occipital 
region  of  the  cranium. 

Power  of  resisting  Shocks. — The  older  French  school  generally 
advocates  the  doctrine  that  the  cranium  resists  shocks  after  the  manner 
of  other  spheres,  namely,  that  a  blow  struck  on  one  side  is  transmitted 
to  the  opposite  one;  as  when  a  glass  tumbler,  struck  smartly  with  the 
finger  nail,  is  made  to  crack  on  the  opposite  side.  This  they  call  fracture 
by  '  contre-coup.'  But  the  modern  school  contends  that  the  cranium  re- 
sists shocks  like  all  architectural  arches;  and  that  vibrations,  instead  of 
going  round  to  the  base  direct,  are  lost  upon  the  supporting  pillars.  The 
frontal  pillars  are  the  malar  and  sphenoid  bones — the  parietal  pillars  are 
the  temporal  bones— the  occipital  pillars  are  the  ribs  of  the  occipital  bone 
itself.  When  the  head  is  struck,  the  parietal  region  is  most  often  the 
seat  of  injury.  The  bone  breaks  at  the  part  struck,  and  the  fracture  runs 
on  through  the  temporal  bone,  and  most  frequently  through  the  tympa- 
num— the  weakest  part.  There  are  many  excavations  in  the  bone  which 
weaken  it  about  this  part;  1,  there  is  the  'meatus  auditorius  externus' 
—2,  the  cavity  of  the  tympanum  itself— 3,  the  jugular  fossa — 4,  the 
carotid  canal — 5,  the  Eustachian  tube.  This  accounts  for  the  frequency 
of  haemorrhage  from  the  ear  in  cases  of  fracture  of  the  base  of  the  skull. 


112  HUMAN    OSTEOLOGY. 

Buttresses,  of  the  Upper  Jaw. — In  the  bones  of  the  face  there 
are  two  points  to  be  noticed — 1st,  the  great  strength  of  the  nasal  arch 
(Plate  XXIV.);  2nd,  the  extreme  firmness  of  the  upper  jaw,  fixed  by  its 
three  buttresses  on  each  side — namely,  the  nasal,  the  zygomatic,  and  the 
pterygoid.  The  nasal  buttresses  rest  against  the  internal  angles  of  the 
frontal  bone,  and  between  them  is  the  heart-shaped  opening  of  the  nose. 
The  zygomatic  buttresses  are  exceedingly  strong;  they  are  supported  by 
the  external  angles  of  the  frontal  bone  and  the  zygomatic  processes  of  the 
temporal,  and  correspond  to  the  molar  teeth,  which  have  to  sustain  the 
greatest  pressure.  The  pterygoid  buttresses  descend  perpendicularly  from 
the  base  of  the  skull,  and  support  the  upper  jaw  behind. 

Male  and  Female  Crania. — The  capacity  of  the  cranial  cavity 
varies,  as  a  general  rule,  with  the  intelligence  of  the  individual  or  of  the 
race.  It  has  been  shown  that  in  almost  all  races  the  capacity  of  the 
cranial  cavities  of  the  women  is  to  that  of  the  men  as  9  is  to  10.  The 
mastoid  and  the  other  processes  for  the  attachment  of  muscles  are  less 
pronounced  in  women  than  in  men.  The  orbital  margins,  and  especially 
the  external  angular  processes,  are  thinner  and  sharper  in  females'  skulls. 
In  women's  skulls  the  glabella  and  frontal  sinuses  are  but  slightly  de- 
veloped. The  digastric  groove  is  better  marked  in  males  than  in  females. 
The  masticatory  apparatus  is  more  massive  in  the  males'  skulls.  The 
development  of  the  frontal,  parietal,  and  occipital  regions  may  be  taken 
as  a  general  expression  of  the  development  of  the  corresponding  lobes, 
of  the  brain.  Upon  this  is  founded  the  study  of  Craniology. 8T 

Facial  Angle. — The  best  method  of  determining  the  proportions 
between  the  cranium  and  face  in  man,  and  the  vertebrate  animals  gen- 
erally, is  by  taking  what  is  called  the  'facial  angle.'  Let  a  line  (see  Fig. 
24)  be  drawn  from  the  external  auditory  meatus  along  the  floor  of  the 
nostrils,  and  be  intersected  by  another  line  touching  the  most  prominent 
parts  of  the  forehead  and  upper  jaw:  the  intercepted  angle  is  generally 

67  Craniology  is  nothing  new.     An  Italian  poet  in  the  age  of  Dante  writes: — 
Nel  Capo  son  tre  celle, 
Et  io  dir6  di  quelle, 
Daxanti  6  lo  intelletto 
E  la  forza  d'  apprendere; 
In  mezzo  6  la  ragione 
E  la  discrezione, 
Che  scerne  buono  e  male. 
Indietro  stS  con  gloria 
La  valente  memoria,  etc.  etc. 


GENERAL    OBSERVATIONS    ON    THE    SKULL.  113 

in  proportion  to  the  size  of  the  cranial  cavity,  and  is  a  measure  of  the  de- 
gree of  intelligence  of  the  individual.  In  the  dog  this  angle  is  20°;  in  the 
chimpanzee,  it  is  40°;  in  the  Australian 
native,  85°;  in  the  European,  95°.  The 
ancients,  in  their  impersonation  of  the 
beautiful  and  intellectual,  adopted  an 
angle  of  100°. 68 

Comparative  Osteology.. — A  stu- 
dent may,  with  careful  observation,  dis- 
cover slight  points  of  difference  between 
opposite  sides  of  the  same  skull.  For  in-  0 

L     .  -,,.-,•  ,         FIG.  34.— Facial  Line  and  Angle. 

stance,  the  posterior  condyloid  foramen  of 

one  side  may  be  wanting,  the  mastoid  process  of  one  side  may  be  larger  than 
that  of  the  other,  or  the  digastric  fossae  may  be  of  unequal  size;  one  nasal 
passage  may  be  larger  than  the  other;  the  lateral  sinus  may  be  much  deeper 
on  the  one  side  than  on  the  other,  or  there  may  be  a  middle  clinoid  pro- 
cess on  one  side  only.  Asymmetry  may  occur  in  men  highly  gifted,  as  in 
the  celebrated  French  anatomist  Bichat.  This  is  no  more  than  one  might 
expect,  seeing  the  difference  often  existing  between  features  of  the  two 
sides  of  the  same  face.  Such  want  of  symmetry  is  greatly  exaggerated  in 
many  of  the  lower  animals*  as  may  be  seen  in  the  Cetacea,  in  the  head  of 
the  great  sperm-whale  or  in  that  of  the  narwhal  (Mus.  Roy.  Coll.  Surg.), 
for  the  details  of  which,  see  the  comparative  osteology  of  the  superior 
maxillary  bone.  But  the  most  striking  example  of  asymmetry  is  seen  in 
those  flat  fish  which  lie  usually  on  their  left  sides,  viz.,  soles  and  plaice 
(Pleuronectidae,  Nos.  179  to  190).  For  in  them  both  eyes  are  on  the 
right  or  upper  side  of  the  skull,  and  one  orbit  only  is  completed,  the  eyes 
being  directed  away  from  the  ground  on  which  they  lie.  The  teeth  are 
chiefly  developed  on  the  left  side  of  their  jaws — away  from  the  side  on 
which  their  eyes  are — that  is,  on  the  white  side.  It  is  interesting  to  note 
that  in  these  fish,  when  very  young,  the  skulls  are  symmetrical.  When 
the  turbot  is  just  hatched,  it  has  an  eye  on  each  side  of  the  head,  and  it 
is  only  by  subsequent  development  that  the  asymmetry  occurs.  The 
turbot,  unlike  soles  and  plaice,  lies  on  its  right  side. 

Different  habits  develop  different  muscles;    and  these   muscles  give 

68  Froriep  ('  Charakteristik  des  Kopfes,' Berlin,  1845)  gives  tables  showing  the 
relative  size  of  the  cranium  and  face  in  infancy,  childhood,  and  adult  age.     They  go 
to  prove  that  the  base  of  the  skull,  and  the  face,  as  contrasted  with  the  capacity  of 
the  cranium,  increase  from  infancy  to  old  age. 
8 


114  HUMAN    OSTEOLOGY. 

rise  to  modifications  in  the  form  of  the  bones  as  well  as  of  the  bodily  con- 
figuration. It  will  therefore  be  extremely  interesting  to  contrast  the 
skulls  of  the  Carnivora  with  those  of  the  Ungulata,  or  hoofed  animals. 
Take,  for  example,  a  tiger's  skull  and  that  of  a  deer.  The  skull  of  the 
tiger  is  in  perfect  adaptation  to  his  enormous  temporal  muscle.  It  has  a 
high  median  ridge,  to  which  the  muscles  are  attached,  great  arches  of  the 
zygoma,  under  which  they  pass,  and  broad  and  lofty  coronoid  processes, 
into  which  they  are  inserted.  But  his  masseters  are  comparatively  small, 
therefore  the  zygomata  and  the  angles  of  the  jaw  are  not  specially  strong. 
Now,  the  sole  action  of  this  temporal  muscle  is  to  clench  the  teeth  to- 
gether as  on  a  hinge;  so  we  find  that  his  jaw  articulation  is  hinge-like, 
and  allows  no  other  motion.  This  mechanism  is  admirably  fitted  for 
cutting  purposes,  but  is  quite  unfit  for  grinding;  so  his  teeth  are  cut- 
ters. He  has  no  grinders.  Exactly  the  converse  of  all  this  is  true  of  the 
deer:  his  temporals  are  small,  he  has  no  median  ridge,  the  passage  under 
the  zygoma  is  small,  and  his  coronoid  process  is  delicate  and  scarcely 
deserves  notice.  On  the  other  hand,  his  masseters  and  pterygoid  muscles 
are  very  large,  his  zygomata  broad,  the  external  pterygoid  plates  greatly 
expanded,  the  angles  of  the  jaw  massive  and  extensive.  The  masseters 
acting  with  the  internal  pterygoids  cause  the  grinding  action;  so  here 
the  articulation  of  the  jaw  is  nearly  flat,  allowing  of  a  free  grinding  move- 
ment; and  in  accordance  with  this,  we  find  the  teeth  are  flattened  on  the 
surface,  and  good  grinders.  It  will  be  seen  how  clearly  this  conforma- 
tion is  in  keeping  with  the  habits  and  nature  of  each  animal. 

From  what  has  been  said  of  the  temporal  muscles  of  the  tiger,  as  well 
as  from  what  will  be  said  of  the  pectoral  muscles  of  the  flying  birds  (Car- 
inatae),  it  appears  that  those  sets  of  muscles  by  which  an  animal  gets  its 
living  are  the  most  largely  developed,  and  that  their  bony  attachments 
are  large  in  proportion.  Thus  the  history  of  the  animal  is  always  writ- 
ten on  its  bones  clearly  enough  for  any  careful  student  to  read.  He  who 
learns  to  love  osteology  will  soon  feel  that  it  is  far  from  dry,  and  that 
beauty  finds  indelible  expression  even  in  the  bones;  for  he  will  see  that 
low  degraded  types  have  skeletons  which  cannot  be  mistaken,  while  the 
healthy,  intelligent,  and  upright  carry  their  characters  in  their  skeletons 
as  much  as  they  do  in  their  faces. 

In  the  ant-eater,  which  has  no  teeth,  the  zygomatic  arch  is  incomplete 
(No.  2336). 

In  reptiles  the  cranial  cavity  is  remarkably  small.     In  a  Nilotic  croco- 


GENERAL    OBSERVATIONS    ON    THE    SKULL.  115 

dile  (No.  717  D)  nearly  fifteen  and  a  half  feet  long,  the  cranial  cavity  is 
only  just  large  enough  to  admit  the  thumb. 

Some  heads  are  long,  some  are  broad,  and  others  round.  These  dif- 
ferent forms  are  determined  by  the  varying  extent  of  growth  of  bone 
either  in  the  transverse  or  the  longitudinal  sutures,  or  by  the  early  union 
of  one  or  other  of  them,  as  may  be  readily  understood  by  a  reference  to 
the  Gen.  Ost.  Ser.  (Nos.  126 — 127),  where,  the  parietal  bones  uniting 
early,  the  skull  was  unable  to  accommodate  the  growing  brain  by  increas- 
ing in  breadth,  and  therefore  could  only  increase  in  length  by  growing 
at  the  fronto-parietal  and  the  occipito-parietal  sutures,  thus  giving  rise 
to  these  extraordinary  long  skulls. 

The  great  and  heavy  skull  of  the  crocodile  contains  large  nasal  pas- 
sages and  air  cavities  which  float  it,  so  that  its  body  can  lie  under  water 
while  its  eyes  and  nostrils  alone  appear  just  above  the  surface  (No.  712). 

One  of  the  first-fruits  of  the  study  of  comparative  anatomy  was  the 
discovery  of  the  law,  '  That  an  invariable  co-relation  exists  not  only  be- 
tween the  different  parts  of  an  animaFs  body,  but  likewise  between  the 
parts  of  his  body  and  his  mode  of  life.'  The  discovery  was  made  by 
Cuvier,  and  would  of  itself  have  been  sufficient  to  immortalize  his  name. 
He  was  led  to  the  detection  of  this  law  by  the  study  of  a  number  of 
fossil  bones  which  were  found  in  quarries  in  the  neighborhood  of  Paris. 
The  following  is  his  own  account: — 89 

'  I  found  myself  in  the  position  of  a  man  who  had  received  a  confused 
heap  of  the  mutilated  and  incomplete  remains  of  some  hundreds  of  skel- 
etons, belonging  to  a  score  of  different  kinds  of  animals;  each  bone  had 
to  search  for  those  with  which  it  should  articulate — it  seemed  almost 
a  resurrection  in  miniature.  I  had  not  at  my  command  the  all-powerful 
trumpet,  but  the  immutable  laws  prescribed  to  living  beings  answered  its 
purpose,  for  at  the  voice  of  comparative  anatomy  every  bone,  every  frag- 
ment of  bone,  resumed  its  natural  position.  I  am  at  a  loss  for  words 
to  describe  my  delight  when  so  soon  as  I  discovered  any  characteristic 
feature,  I  saw  all  the  sequences  of  this  character,  more  or  less  foreseen, 
develop  themselves  in  succession.  I  found  the  teeth  conformed  to  what 
the  feet  had  foretold,  and  the  feet  to  what  the  teeth  foretold,  and  all  the 
bones  between  the  feet  and  the  teeth  conformed  as  could  be  judged  be- 
forehand; in  a  word,  each  of  these  species  sprang  up  again  out  of  one 
of  its  elements.  Those  who  will  have  the  patience  to  follow  me  will  be 
69  Cuvier,  '  Recherches  sur  les  ossemens  fossiles,'  1822,  vol.  ii.  p.  231. 


116  HUMAN   OSTEOLOGY. 

able  to  form  an  idea  of  the  sensations  I  experienced  in  thus  restoring 
by  degrees  these  antique  monuments  of  fearful  revolutions.  Subse- 
quent discoveries  of  fossils  have  hardly  ever  contradicted  my  earlier  con- 
clusions.' 


THE  VERTEBRAL  COLUMN. 

(PLATES  XXV.   TO  XXIX.) 

The  vertebral  column,  or  spine  (Plate  XXVI.),  consists  of  a  series  of 
bones  articulated  together  so  as  to  describe  three  slight  and  graceful 
curves,  the  bend  being  forward  in  the  loins,  backward  in  the  chest,  and 
again  forward  in  the  neck.  These  bones  are  called  '  vertebrae/  because 
they  permit  the  bending  and  rotation  of  the  body  (verto,  I  turn).  They 
are  33  in  number:  of  which  7  constitute  the  cervical  region,  12  the 
dorsal,  and  5  the  lumbar.  Below  the  lumbar  vertebrae,  the  spine  is  sup- 
ported upon  a  bone  termed  the  '  os  sacrum/  which  consists  of  five  verte- 
brae firmly  coalesced  into  a  single  bone.  Below  the  sacrum  is  the  little 
bone  termed  the  '  coccyx/  from  its  resemblance  to  the  beak  of  a  cuckoo 
(KOKKV%}.  This  also  contains  the  rudiments  of  four,  sometimes  only 
three,  vertebrae.  The  vertebral  formula  of  man,  therefore,  is — 7  cervi- 
cal, 12  dorsal,  5  lumbar,  5  sacral,  and  4  coccygeal,  or  caudal:  that  is,  33 
in  all. 

Constituent  Parts  of  a  Vfertebra.— The  vertebrae  have  certain 
general  characters  which  are  common  to  all.  These  are  modified  in  the 
different  regions  of  the  spine,  according  to  the  functiong  they  perform. 
(See  separate  series,  Mus.  Roy.  Coll.  Surg.)  Therefore,  first  obtain  a 
general  knowledge  of  a  vertebra,  and  of  the  names  given  to  its  several 
parts;  afterward  examine  the  characteristics  of  the  vertebras  in  each 
region. 

Taking  the  first  lumbar  vertebra  as  a  pattern  (Plate  XXV.),  it  is  seen 
to  consist  of  a  '  body/  or  '  centrum/  which  forms  the  columnar  part,  and 
supports  the  weight  of  the  spine.  The  body  is  convex  in  front  from  side 
to  side,  but  slightly  concave  behind,  where  it  assists  in  the  formation  of 
the  '  vertebral  foramen/  which  transmits  and  protects  the  spinal  cord. 
The  upper  and  lower  surfaces  of  the  body  present  a  disc  of  solid  bone  at 
the  circumference  (Plate  XXV.  Fig.  2),  and  a  slight  cup  in  the  centre 


tiwls 


•  process. 


Supv -tubercle 


InFtuberc 


art'icular  pnoces 
Lumbar  Vertebra. 


A.-rticulailon  for  Ri 


Section  sliowin^ Venous  canals. 

pT  articular  process 


Articulation  fbrEib. 
Transverse  process- 


Articulation  for  Rib 
Inferioc  artmular  process 


Dorsal  Yertetra, 


oramerr  i^Vertetral  Arler  \f 
PosLr*l\jterc1e  of  TraJisverse  process 

Sup1- articular  process. 
InFr  arti  cular-process. 


Spraous  pro  cess  k 
Cervical  "Vertetra. 


PLATE  XXV 


ntr  Tubercle 


or  OdonbH  process. 


.Transverse  process. 

Foramen  for  Vertebral  Artery: 
Groove  for  Vertebral  Artery. 


SpinoBS  process. 
Tirst  Cervical  Vertebra  or  Atlas. 


Arbicular  surface  for  Atlas  j|l      l-Odontoid  process 


rticular 

Pace.  VForamenfop^rbsbral  Anfcery 


Transverse  p 
Inffarticula 

Second  Cervical  Vertebra.!  or.  Axis. 


ansverse  process 


Lumlar  "Vertebra. 


THE    VERTEBRAL    COLUMN.  117 

which  lodges  the  elastic  '  intervertebral  fibro-cartilage/  found  in  the  recent 
subject,  and  acting  as  a  '  buffer '  between  the  vertebrae.  These  discs  or 
rings  of  compact  bone  deserve  notice,  not  only  because  they  strengthen  the 
spongy  bodies,  but  because  they  have  separate  centres  of  ossification,  and 
remain  until  about  the  25th  year,  as  '  epiphyses/  A  section  through  the 
body  of  a  vertebra  shows  it  to  be  composed  of  cancellous  tissue,  which 
makes  it  light  compared  to  its  bulk.  (Nor.  Hum.  Ost.,  Nos.  175  to  185.) 
This  tissue  is  traversed  by  large  *  venous  canals,'  of  which  the  orifices  are 
observable  on  the  surface,  but  chiefly  on  the  back  part  of  the  body,  toward 
which  the  larger  canals  converge  (Plate  XXV.  Fig.  7).  Behind  the 
body  is  the  '  vertebral  foramen.'  Now  this  foramen  is  formed  by  two 
thick  processes  of  bone,  which  proceed,  one  from  each  side  of  the  poste- 
rior part  of  the  body,  and  gradually  converging,  unite  and  form  an  arch 
(vertebral  or  neural  arch).  The  spring  of  the  arch,  where  it  joins  the 
body,  is  called  the  '  pedicle ' ;  the  converging  plates  are  termed  the  '  lami- 
nae.' The  arch  sends  off  seven  'processes.'  Of  these,  three — namely,  the 
'  spinous '  and  the  two  *  transverse ' — give  attachment  to  muscles.  The 
'  spinous  process '  arises  from  the  top  of  the  arch;  the  two  '  transverse 
processes'  pass  off,  nearly  horizontally,  one  from  each  side  of  it,  near  the 
junction  of  the  'pedicle*  with  the  'lamina.'  The  remaining  four  are 
termed  '  articular  processes ' — two  superior  articulating  with  corresponding 
processes  of  the  vertebra  above  and  two  inferior  articulating  with  corre- 
sponding processes  of  the  vertebra  below;  they  are  situated  on  the  point 
of  union  of  the  pedicles  with  the  laminas.  Their  articular  surfaces  are 
covered  with  cartilage  in  the  fresh  state,  and  project  beyond  the  bodies, 
so  that  the  joints  are  on  a  level  with  the  intervertebral  nbro-cartilages. 
Lastly,  on  the  pedicles,  we  observe  two  '  notches'  on  either  side, — an  upper 
and  a  lower,  the  lower  being  always  the  larger.  When  the  vertebrae  are 
together,  these  notches  make  what  are  called  the '  intervertebral  foramina/ 
in  which  the  spinal  nerves  lie.  (Plate  XXVII.)  The  '  pedicle/  or  the 
part  of  the  arch  between  the  notches,  is  the  weakest  part  of  a  verte- 
bra, and  consequently  it  is  the  principal  seat  of  torsion  in  curvatures  of 
the  spine. 

Such,  then,  are  the  constituent  parts  of  a  vertebra:  namely,  a  body, 
an  arch,  a  vertebral  foramen:  seven  outstanding  processes,  of  which  four 
are  articular,  and  three  give  attachment  to  muscles;  lastly,  the  notches 
which  transmit  the  spinal  nerves. 

In  examining  a  single  vertebra  it  is  necessary  first  to  ascertain  to 


118  HUMAN    OSTEOLOGY. 

which  region  it  belongs,  and  then  which  vertebra  it  is  of  that  region. 
We  will  therefore  describe  first  the  distinctive  characters  of  the  region, 
and  then  the  peculiar  characters  of  the  individual  vertebrae,  as  far  as 
they  can  with  certainty  be  distinguished. 

Cervical  Vertebrae — Distinctive  Character. — All  the  cervical 
vertebras,  and  they  alone,  have  a  foramen  in  the  base  of  each  transverse 
process,  which  (excepting  that  in  the  7th)  transmits  the  vertebral  vessels 
and  a  plexus  of  sympathetic  nerves. 

General  Characters  of  the  Cervical  Vertebrae. — There  are  seven 
cervical  vertebrae.  The  '  bodies,'  excepting  the  first  and  second,  are 
broader  from  side  to  side  than  from  before  backward,  and  a  lateral  ridge 
projects  from  each  side  of  their  upper  borders,  and  fits  into  a  corre- 
sponding depression  on  the  sides  of  the  vertebra  above  (Plate  XXV. 
Fig.  4).  Each  'body'  slopes  a  little  forward,  and  overlaps  the  one  below. 
(Plate  XXVII.)  By  all  this  interlocking,  lateral  displacement  is  pre- 
vented; this  mechanism  compensating  for  the  apparently  insecure  con- 
nections of  the  articular  processes.  Their  '  spinous  processes '  are  hori- 
zontal, and  give  attachment  to  the  ligamentum  nuchse  as  well  as  to  the 
muscles  .which  maintain  the  head  erect.  But  the  spinous  processes  of 
the  third,  fourth,  and  fifth  are  especially  short,  and  permit  the  free  ex- 
tension of  the  neck,  and  are  very  distinctly  bifurcated;  they  overlap  each 
other  a  little  in  extension,  as  any  one  may  see  in  the  dry  bones  by  mov- 
ing them  backward  over  each  other.  There  is  a  groove  on  the  upper  sur- 
face of  each  transverse  process  in  which  lodges  the  spinal  nerve;  and 
this  groove  bifurcates  the  summit,  so  that  there  are  two  '  tubercles ' 
formed,  an  anterior  and  a  posterior  (in  the  lower  five),  both  for  the  at- 
tachment of  muscles,  Observe  especially  the  large  size  of  the  anterior 
tubercle  of  the  sixth  cervical  vertebra.  It  is  called  the  carotid  tubercle, 
being  a  guide  to  the  carotid  artery.  Strictly  speaking,  we  ought  to  say 
that  the  transverse  process  of  a  cervical  vertebra  arises  by  two  roots  or 
bars,  an  anterior  and  a  posterior,  which  subsequently  join,  and  so  form 
the  foramen  which  transmits  the  vertebral  artery,  vein,  and  a  plexus  of 
nerves:  the  anterior  root  springs  from  the  side  of  the  body:  the  posterior 
springs  from  the  arch.  Their  '  articular  processes '  are  flat,  oblique,  and  in- 
clined, so  that  their  planes  make  an  angle  of  about  45°  with  the  horizon. 
The  upper  processes  look  backward  and  upward,  the  lower  forward  and 
downward.  Their  obliquity  permits  the  requisite  flexion  and  extension 
of  the  neck,  as  well  as  slight  lateral  inclination  of  it.  A  dislocation  of  one 


THE    VERTEBRAL    COLUMN.  119 

of  these  vertebrae  may  happen  without  fracture  of  the  articular  processes. 
Such  a  dislocation  is  exceedingly  rare;  but  there  are  specimens  of  it  in  the 
Museum  of  St.  Bartholomew's  Hospital.  It  may  be  produced  by  sudden 
and  forcible  rotation  of  the  neck.  Baron  Boyer  70  speaks  of  an  advocate 
who  dislocated  one  of  his  cervical  vertebrae  by  suddenly  turning  his  head 
round  to  see  who  was  coming  in  at  a  door  behind  him. 

1st  and  2nd  Cervical  Vertebrae. — The  1st  and  2nd  cervical  verte- 
brae differ  most  remarkably  from  the  rest,  as  they  respectively  permit  the 
nodding  and  the  rotation  of  the  head. 

1st  Cervical  Vertebra:  Atlas.— The  1st  cervical  vertebra  (Plate 
XXV.  Fig.  5)  is  called  the  '  atlas, '  because  it  supports  the  head.  This  is 
the  only  vertebra  which  has  no  body.  The  odontoid  process  of  the  axis 
(the  2nd  cervical  vertebra)  is  the  body  of  the  atlas,  and  is  thus  transferred 
and  fixed  to  the  second  vertebra,  forming  a  pivot  or  axis  upon  which 
the  atlas  rotates.  It  seems,  at  first  sight,  rather  far-fetched  to  say  that 
the  atlas  rotates  round  its  own  body  (detached);  but  it  is  nevertheless 
true,  and  borne  out  by  the  facts  of  philosophical  anatomy.  The  '  spinous 
process '  is  a  mere  tubercle  (the  posterior  tubercle)  to  which  the  '  rectus 
capitis  posticus  minor '  is  attached.  A  large  spine  here  would  interfere 
with  the  free  backward  movement  of  the  head.  This  vertebra  is  like 
a  ring,  wider  behind  than  in  front,  and  thickened  on  each  side,  forming 
the  '  lateral  masses '  and  the  articular  surfaces.  In  front  there  is  a  small 
*  anterior  tubercle/  into  which  is  inserted  a  portion  of  the  '  lougus  colli/ 

Now  the  form  of  the  atlas  is  adapted  to  the  rotatory  movement  of  the 
head.  In  the  first  place  there  is  a  little  articular  surface,  the  odontoid 
articulation,  on  the  back  of  the  anterior  part  of  the  ring  of  the  atlas. 
The  '  transverse  processes '  are  thick  and  strong,  and  project  far  beyond 
those  of  the  other  cervical  vertebrae,  and  give  great  leverage  to  the  infe- 
rior oblique  muscles  which  assist  in  rotating  the  head  from  side  to  side. 
Its  '  inferior  articular '  processes  look  downward  and  slightly  inward;  they 
are  nearly  horizontal,  flat  and  circular,  like  the  upper  ones  on  the  axis 
on  which  they  slide,  in  the  movement  of  rotation  of  the  head.  The 
'  superior  articular  surfaces '  are  concave,  and  articulate  with  the  convex 
condyles  of  the  occipital  bone,  and  are  similarly  oval,  converge  ante- 
riorly, and  lie  near  the  front  of  the  foramen.  The  outer  edges  being  the 
highest,  they  form  two  little  cups  looking  upward  and  inward,  which 
receive  the  occipital  condyles,  sustain  the  whole  weight  of  the  head,  and 
"°  '  Traite  des  Malad.  Chir.'  t.  iv.  c.  iv. 


120  HUMAN    OSTEOLOGY. 

permit  its  nodding  movement.  On  the  inner  side  of  each  articular  pro- 
cess is  a  tubercle  which  gives  attachment  to  the  strong  '  transverse '  liga- 
ment, which  confines  the  odontoid  process  in  its  position.  The  '  arch ' 
formed  by  the  laminae  is  wider  than  in  other  vertebrae,  and  leaves  such 
ample  space  that  lateral  displacement  of  the  atlas  has  occurred  without 
compression  of  the  spinal  cord.71  On  the  upper  surface  of  each  lamina 
is  a  groove  (sometimes  a  complete  bony  canal)  for  the  vertebral  artery 
and  suboccipital  nerve;  this  corresponds  to  the  superior  notch  in  the  other 
vertebras.  Lastly,  the  '  notches '  for  the  nerves  are  placed  behind  the  ar- 
ticular processes,  while  in  all  the  other  vertebrae  (except  the  upper  notch 
in  the  axis)  they  are  in  front  of  them. 

2nd  Cervical  Vertebra:  Axis. — The  2nd  cervical  vertebra  or 
'  vertebra  dentata '  (Plate  XXV.  Fig.  6)  is  called  the  '  axis '  because  it  is 
the  axis  upon  which  the  atlas  (with  the  head)  rotates.  The  pivot,  termed 
the  '  odontoid  process '  from  its  resemblance  to  a  tooth,  rises  vertically 
from  the  '  body '  of  the  axis,  and  fits  into  a  ring  formed  in  front  by  the 
atlas,  and  behind  by  the  strong  '  transverse '  ligament  which  passes  be- 
tween the  lateral  masses  of  the  atlas,  and  divides  the  vertebral  foramen 
of  that  bone  into  two  parts,  an  anterior  for  the  reception  of  the  odontoid 
process,  and  a  posterior  for  the  passage  of  the  spinal  cord.  It  is  a 
mechanism  resembling  a  tenon  and  mortise.72  The  odontoid  process  has 
a  smooth  surface  in  front,  which  articulates  with  the  atlas;  another  be- 
hind, on  which  plays  the  ligament.  There  is  a  distinct  synovial  mem- 
brane and  a  layer  of  cartilage  on  each  surface,  so  that  they  possess  all  the 
apparatus  of  a  joint.  Moreover,  it  is  slightly  constricted  at  its  lower 
part  (forming  what  is  called  '  the  neck '),  which  the  '  transverse '  ligament 
clasps  securely.  Lastly,  its  summit  or  '  head '  is  rough  and  sloped  later- 
ally. From  these  lateral  slopes  proceed  the  '  check '  or  '  odontoid '  liga- 
ments, which  fasten  the  odontoid  process  to  the  occipital  bone.  Not- 
withstanding the  strength  of  its  ligaments,  the  odontoid  process  does 
sometimes  slip  out  of  its  ring.  The  following  is  an  instance: — A  lady 
was  carrying  her  child  on  her  shoulders.  Losing  its  balance,  the  child 
clung  to  its  mother's  head,  and  drew  it  suddenly  and  forcibly  backward. 
The  lady  fell  dead.  It  is  more  liable  to  dislocation  in  children,  because 
the  ligaments  are  weaker  than  in  the  adult.  Petit  relates  the  case  of  a 

11  See  a  case  of  this  kind,  with  a  drawing,  in  '  Med.  Chir.  Trans. '  vol.  xxxi.,  by  Sir 
James  Paget. 

72  '  Natural  Theology.      Paley 


THE    VERTEBRAL    COLUMN.  121 

child  who  was  instantaneously  killed  by  being  lifted  by  the  head.  Con- 
sidering the  importance  of  the  odontoid  process,  we  are  not  surprised  that 
its  internal  structure  is  much  more  compact  than  that  of  the  body  of  the 
axis.  The  upper  '  articular  processes '  are  placed,  partly  on  the  body  and 
partly  on  the  root  of  each  transverse  process;  they  are  nearly  flat  and 
circular,  and  slope  a  little  downward  and  outward.  Like  those  of  the 
first  vertebra,  they  have  a  very  strong  base,  and  transmit  to  the  '  body  ' 
the  weight  of  the  head.  The  *  notch '  is  behind  them.  The  lower  *  ar- 
ticular processes '  are  oblique,  and  placed  considerably  behind  the  upper, 
and  correspond  with  the  line  of  the  articular  processes  of  the  succeeding 
vertebra  which  they  resemble.  The  intervertebral  '  notch '  is  in  front  of 
them,  as  in  all  the  vertebras  below.  The  '  transverse  processes '  are  com- 
paratively small,  and  not  grooved  or  bifurcated;  but  the  hole  at  their 
base  is  inclined  oliquely  outward,  corresponding  to  the  curve  of  the  verte- 
bral artery.  The  '  laminae '  of  the  arch  are  remarkably  strong.  The 
*  spinous  process '  stands  well  out,  and  bifurcates  widely,  giving  great 
leverage  to  the  inferior  oblique  muscles  which  rotate  the  head.  The  great 
size  and  projection  of  this  spinous  process  is  one  of  the  distinguishing 
characters  of  the  axis;  and  with  this  we  should  associate  the  large  size  of 
the  transverse  processes  of  the  atlas,  these  being  the  respective  attach- 
ments of  the  inferior  oblique  muscles. 

3rd,  4th,  and  5th  Cervical  Vertebrae.— The  3rd,  4th,  and  5th  cer- 
vical vertebrae  can  be  easily  distinguished  from  the  rest,  although  not 
from  one  another,  by  the  following  points  : — Their  spinous  processes  are 
spread  out  horizontally,  and  are  thin,  bifid,  and  short  (Plate  XXV. 
Pig.  4),  thus  allowing  the  neck  to  be  bent  backwards  very  considerably 
before  the  spines  come  into  contact. 

6th  Cervical  Vertebra. — The  spine  of  the  6th  is  short,  it  is  not 
bifid  (or  rarely  so),  and  runs  nearly  horizontally  backward,  but  is  not 
spread  out  like  the  3rd,  4th,  and  5th. 

7th  Cervical  Vertebra. — The  7th  cervical  is  called  the  '  vertebra 
prominens '  on  account  of  its  long  and  prominent  spine,  which  can  be 
easily  felt  at  the  back  of  the  neck.  It  slopes  downward,  and  thus  some- 
what resembles  those  in  the  dorsal  region,  and  gives  attachment  to  the 
'  ligamentum  nuchae.'  The  foramen  in  the  transverse  process  is  never 
traversed  by  the  vertebral  vessels,  and  is  in  some  rare  cases  absent.  More- 
over, the  transverse  processes,  though  so  long  and  broad  as  to  suggest  a 
rudimentary  rib,  are  but  slightly  grooved,  and  have  no  distinct  tubercles. 


122  HUMAN    OSTEOLOGY. 

This  vertebra  in  some  rare  instances?  has  two  little  (cervical)  ribs  attached 
to  it,  one  on  either  side,  in  form  and  situation  resembling  the  cervical 
ribs  of  animals.  A  cervical  rib  may  be  mistaken  for  a  bony  tumor  if 
the  surgeon  does  not  bear  in  mind  that  such  an  anomaly  may  exist  in 
the  skeleton.  It  is  sometimes  united  with  the  first  rib. 

Dorsal  Vertebrae:  Distinctive  Character. — All  the  dorsal  verte- 
brae, and  they  alone,  have  facets  on  the  sides  of  their  bodies  with  which 
the  heads  of  the  ribs  articulate. 

Dorsal  Vertebrae:  General  Characters. — The  general  characters  of 
the  twelve  dorsal  vertebrae  are  as  follows: — Their  '  bodies '  are  heart-shaped, 
and  smaller  than  those  of  the  lumbar,  and  they  have  less  weight  to  bear. 
Their  vertical  depth  is  less  in  front  than  behind,  especially  near  the  mid- 
dle of  the  back,  in  adaptation  to  the  dorsal  curve.  They  have  two  little 
cup-like  facets  on  each  side  for  the  articulation  of  the  heads  of  the  ribs, 
the  lower  cups  being  the  larger.  By  referring  to  the  spine  (Plate 
XXVI.),  we  observe  that  the  socket  for  the  head  of  the  rib  is  formed  by 
the  articular  facets  of  two  vertebras  with  the  intervening  fibre-cartilage. 
Their  '  spinous  processes '  are  long,  clubbed  at  the  end  and  slant  down- 
ward, so  that  they  overlap  each  other,  especially  near  the  middle  of  the 
back,  and  prevent  extension  of  the  spine  in  this  region.  Their  '  transverse 
processes '  are  thick  and  strong,  and  each  has  in  front,  near  its  end,  an 
articular  surface  for  the  tubercle  of  a  rib,  which  it  supports  like  a  but- 
tress. Observe  that  the  transverse  processes  of  the  seven  upper  dorsal 
vertebrae  are  very  thick  and  strong,  and  support  the  seven  true  ribs, 
whilst  the  five  lower  gradually  diminish  in  size;  those  of  the  eleventh 
and  twelfth  are  the  smallest  of  all,  and  they  do  not  support  ribs;  these 
lower  ones  present  three  tubercles,  of  which  more  will  be  said  hereafter. 
The  '  laminae '  are  broad  and  flat,  and  slope  one  over  the  other.  Of  the 
'  articular  processes '  the  upper  look  backward,  the  lower  forward,  and  the 
planes  of  both  are  so  nearly  vertical  that  it  is  manifest  there  can  be  but 
little  movement  between  any  two  dorsal  vertebrae.  The  '  vertebral  fora- 
men '  is  nearly  round. 

ist,  pth,  loth,  nth,  and  I2th  Dorsal  Vertebrae. — The  FIEST 
dorsal  vertebra  has  on  the  side  of  its  '  body '  an  articular  surface  for  the 
whole  of  the  head  of  the  first  rib,  and  a  smaller  one  at  the  lower  border 
for  half  of  that  of  the  second  rib.  Again,  the  upper  surface  of  its  body 
has  lateral  ridges  like  the  cervical  vertebrae.  The  NINTH  dorsal  has 
usually  only  half  a  facet  on  the  upper  part  of  the  body.  The  TENTH 


THE    VERTEBRAL    COLUMN.  123 

dorsal  has  generally  an  entire  facet  for  the  tenth  rib.  The  ELEVENTH 
and  TWELFTH  dorsal  have  each  a  single  articular  facet  for  the  eleventh 
and  twelfth  ribs  respectively,  and  their  'transverse  processes/  much 
reduced  in  size,  do  not  articulate  with  the  ribs.  Moreover,  they  are 
smaller  than  in  the  upper  dorsal  region,  and  they  resolve  themselves  into 
three  tubercles  (seen  in  Fig.  25).  The  TWELFTH  dorsal  may  be  dis- 
tinguished from  the  ELEVENTH  by  the  fact  that  its  lower  articular  pro- 


d.  Superior  articular  process.  <J 

a.  Superior  tubercle.  a 


b.  External  tubercle  (rudimentary  trans. 

P.). 


c.  Inferior  tubercle.  0 


e.  Inferior  articular  process. 


FIG.  25.— Twelfth  Dorsal  Vertebra,  showing  the  Three  Tubercles  on  the  Transverse  Processes. 

cesses  look  outward,  like  the  corresponding  processes  in  the  lumbar  ver- 
tebrae. Its  spinous  process  is  short  and  square,  and  more  like  those  of  the 
lumbar  vertebrae.  The  tubercles  of  its  transverse  process  are  always  well- 
marked.  (Plate  XLV.  Fig.  2.) 

Lumbar  Vertebrae:  Distinctive  Characters. — The  lumbar  ver- 
tebras have  neither  holes  in  their  transverse  processes  nor  articulations 
for  ribs. 

General  Characters  of  the  Lumbar  Vertebrae.— The  general 
characters  of  the  five  lumbar  vertebrae  are  as  follows: — The  'bodies'  are 
large  and  oval,  with  their  broad  diameters  transverse,  and  firmly  support 
the  trunk.  The  vertical  measurement  of  the  bodies  is  greater  in  front 
than  behind,  in  adaptation  to  the  lumbar  curve.  Their  sides  are  slightly 
excavated,  which  economizes  weight  and  bulk.  Their  '  spinous  processes ' 
are  broad,  in  their  vertical  measurement,  thickest  at  the  lower  border, 
and  give  good  leverage  to  the  extensor  muscles  of  the  spine:  they  stand 
out  horizontally,  and  so  do  not  interfere  with  the  extension  of  the  back. 


124  HUMAN    OSTEOLOGY. 

Their  '  transverse  processes '  are  thin  and  long,  and  appear  like  stunted 
ribs,  but  are  not  true  ribs.  Their  '  articular  processes'  are  vertical,  and 
very  strong:  the  upper,  slightly  concave,  look  toward  each  other;  the 
lower,  slightly  convex,  are  nearer  together,  and  fit  in  between  the  upper 
ones  of  the  succeeding  vertebra.  Thus,  these  articulations  are  so  shaped 
that  they  admit,  not  only  of  extension  and  flexion  of  the  loins,  but  of  a 
certain  amount  of  rotation,  which  is  useful  in  progression.  The  '  verte- 
bral foramen '  is  triangular,  with  the  angles  rounded. 

Characters  of  the  last  Lumbar  Vertebra.— The  last  lumbar 
vertebra  is  distinguished  (1)  by  the  slope  on  the  lower  surface  of  its  body, 
in  adaptation  to  the  slope  of  the  sacrum;  (2)  by  the  great  thickness  of 
the  root  of  its  transverse  process  which  springs  more  from  the  body,  the 
ilio-lumbar  ligament  being  attached  to  this  additional  massiveness;  (3) 
by  its  lower  articulating  processes  being  placed  so  widely  apart;  and  (4) 
by  its  spinous  process  being  somewhat  reduced  in  size,  thereby  leaving 
room  for  the  free  extension  in  this  part  of  the  back. 

Tubercles  on  the  Lower  Dorsal  and  Lumbar  Vertebrae. — 
An  observant  eye  looking  at  the  back  of  a  well-marked  spinal  column 
will  find  that  the  transverse  processes  of  the  lower  dorsal  vertebrae  have  a 
tendency  to  resolve  themselves  into  three  bony  prominences  at  their  ex- 
tremities. The  twelfth  (often  the  eleventh)  transverse  process  actually 
terminates  in  three  such  prominences  or  tubercles;  one  being  superior,  a 
second  inferior,  and  a  third  external  (see  Fig.  25).  The  '  superior  tuber- 
cle '  is  close  behind  the  superior  articular  process.  The  '  inferior  tubercle ' 
is  in  a  straight  line  immediately  below  the  superior;  the  '  external '  pro- 
jects in  front  of  the  other  two  tubercles,  and  is  seen  to  be  in  a  line 
with  that  part  of  the  transverse  processes  of  the  upper  dorsal  vertebra 
which  bears  the  ribs.  Now  the  superior  and  inferior  tubercles  gradually 
fade  away  in  the  lumbar  vertebrae;  but  the  external  tubercle  increases  in 
size,  and  forms  the  transverse  process  of  the  lumbar  region.  Hence  the 
transverse  process  of  a  human  lumbar  vertebra  is  homologous  to  that  part 
of  the  transverse  process  of  a  typical  dorsal  vertebra  which  articulates  with 
the  tubercle  of  a  rib.  The  tubercles  are  shown  in  Plate  XLV.  Fig.  2. 

In  the  human  subject  these  '  tubercles ' 7S  serve  only  as  attachments  for 

73  The  inferior  tubercles  are  alluded  to  by  Monro,  '  Anatomy  of  the  Human 
Bones,'  1726;  also  by  Soemmering,  '  De  Corp.  Human.  Fabrica, '  8vo.  1794.  The 
superior  as  well  as  the  inferior  tubercles  are  developed  as  little  epiphyses  with  dis- 
tinct centres  of  ossification,  and  unite  to  the  rest  of  the  vertebrae  about  the  twenty- 
nfth  year. 


THE   VEETEBRAL    COLUMN. 


125 


muscles;  but  in  some  animals  they  attain  extraordinary  size,  and  have 
other  functions.  For  instance:  in  the  armadillo  (No.  ^335  B),  the  su- 
perior tubercle  is  as  long  as  the  spinous  process  itself,  and  helps  to  support 
the  armor.  In  the  Carnivora  the  inferior  tubercles  gain  a  conspicuous 
development  in  the  lower  dorsal  and  upper  lumbar  regions,  and  contribute 
to  the  lateral  security  of  the  spine. 

TABLE  CONTRASTING  THE  IMPORTANT  PARTS  OF  THE  VERTEBRAE  IN. 
THE  DIFFERENT  EEGIONS. 

We  have  shown  how  the  vertebrae  of  the  different  regions  of  the  spinal 
column  may  be  distinguished,  within  certain  limits,  by  the  examination 
of  any  one  of  their  constituent  parts.  These  important  parts  are  con- 
trasted in  the  annexed  table. 

Cervical. — Always  broadest  transversely.     Lateral  ridges 

on  upper  surface. 

Dorsal. — Transverse  and  antero-posterior  measurements 
nearly  equal,  except  in  two  or  three  upper- 
most. Facets  or  parts  of  facets  on  sides  for 
heads  of  ribs. 

Lumbar. — Always  broadest  transversely,  somewhat  kid- 
ney-shaped, no  ridges,  no  facets. 
C  Cervical. — Long,  thin  and  flattened, 
•j  Dorsal. — Short,  very  broad  vertically. 
[  Lumbar. — Very  short  and  stout. 
(  Cervical. — Bifurcated,  grooved  underneath, 
•s  Dorsal. — Long,  very  oblique,  tubercle  at  summit. 
(^  Lumbar. — Broad  and  square. 

Cervical. — Bifurcated,  grooved  on  upper  surface.      Fo- 
ramina for  vertebral  artery. 
Dorsal. — Large  and  strong  ;  facets  for  tubercles  of  ribs, 

except  eleventh  and  twelfth. 
Lumbar. — Thin,  long  and  narrow. 
Cervical. — Surfaces  plane,  inclined  at  angle  of  45°,  look 

backward  and  upward. 
Dorsal. — Surfaces  plane,  almost  vertical,  look  backward 

and  outward. 

Lumbar. — Surfaces  concave,  vertical,  look  backward  and 
inward. 


BODIES  OR 
CENTRA. 


LAMINA. 


SPINES. 


TRANSVERSE 
PROCESSES. 


SUPERIOR 
ARTICULAR 
PROCESSES. 


126  HUMAN  OSTEOLOGY. 

Vertebral  Column  as  a  Whole. — The  spine  is  a  most  wonderful 

piece  of  mechanism.  :nul  has  excited  the  admiration  of  anatomists  in  all 
ages,  from  the  fwious  and  apparently  incompatible  offices  it  serves  (Hate 
\  \  \  I.).  It  forms  a  column,  at  once  strong  and  firm,  which  supports 
the  body  in  the  oivot  position:  it  is  flexible,  and  so  admits  the  bending 
of  the  trunk  in  various  degrees;  it  is  elastic,  diminishing  concussion  of 
the  head.  It  forms  a  continuous  canal  at  the  hack  of  the  column,  which 
contains  and  protects  the  spinal  cord,  a  basis  for  the  origin  of  the  muscles 
which  spread  over  the  trunk,  and  a  lever  for  the  muscles  which  keep  the 
body  erect.  All  these  offices  are  performed  by  it  with  so  much  safety,  that 
even  the  feats  of  a  mountebank  rarely  injure  the  spine. 

Strength  of  the  Spine.— The  main  strength  of  the  spine  depends 
upon  this, — that  it  consists  of  a  chain  of  bones  so  locked  together,  that 
the  degree  of  motion  between  any  two  is  limited,  though  the  sum  of  the 
whole  is  extensive.  Another  reason  of  the  strength  of  the  spine  is  its 
arrangement  in  alternate  curves.  Mathematicians  have  calculated  that 
it  is  many  times  stronger,  and  more  adapted  to  resist  vertical  pressure. 
than  if  it  were  straight,  the  force  being  decomposed  by  the  curves. '• 
Look  at  the  enormous  weight  which  a  man  can  carry  with  ease  and  safety 
on  his  head.  Moreover,  the  curves  convert  the  spine  into  so  many  elastic 
spring*,  which  prevent  the  jarring  of  the  brain.  Besides  this,  the  curves 
are  admirably  disposed  for  the  lodgment  of  the  internal  organs,  and  the 
transmission  of  the  weight  of  the  head  and  trunk  in  the  line  of  gravity. 
They  are  so  regular  and  gentle  withal,  that  the  spinal  cord  runs  no  risk 
of  compression;  and  lastly,  they  give  the  body  that  graceful  form  which 
has  been  the  *  line  of  beauty  '  in  every  age. 

The  weakest  part  of  the  spine  is  about  the  last  dorsal  vertebra:  firstly. 
because  it  is  the  narrowest  part  of  the  column;  secondly,  because  it  is 
not  supported  by  the  ribs  like  the  higher  dorsal  vertebra?:  thirdly,  because 
it  is  the  centre  of  the  spine  and  the  centre  of  motion  in  the  back,  and 
therefore  exposed  to  the  powerful  leverage  of  the  spine  above  and  below 
it.  Again,  at  the  articulation  between  the  last  dorsal  and  the  first  lumbar 
vertebrae,  the  pliable  lumbar  part  of  the  spine  suddenly  joins  the  com- 
paratively rigid  dorsal  region. 

Curves  of  the  Spine.— The  curves  of  the  spine  are  produced  partly 
by  the  relative  thickness  of  the  bodies  of  the  vertebnv  in  the  different 
regions,  but  rAiVjfty  by  the  relative  thickness  of  the  intervertobral  fibro- 
«  Rollin  and  Magendte  make  it  sixteen  times  stronger. 


THE    VERTEBRAL    COLUMN.  127 

cartilages  and  the  tension  and  elasticity  of  the  '  ligamenta  subfiava '  which 
connect  the  laminas. 

Extent  of  Motion  in  Different  Regions. — From  common  obser- 
vation, as  well  as  from  experiments,  it  appears  that  flexion  and  extension, 
as  well  as  lateral  movement  of  the  spiae,  are  freest  in  the  neck,  less  free 
in  the  loins,  and  least  free  in  the  dorsal  region.  Now  the  component 
parts  of  the  vertebras  are  shaped  accordingly.  Thus,  in  the  neck  the 
articular  processes  are  oblique,  the  spinous  processes  of  the  third,  fourth, 
and  fifth  vertebrae  are  short  and  spread  out  horizontally,  and  the  inter- 
vertebral  substances  thick.  In  the  back  these  substances  are  thin,  the 
articular  processes  nearly  vertical,  and  the  spinous  processes  are  long  and 
overlap  each  other,  particularly  about  the  middle  of  the  back,  where  the 
heart  lies,  from  the  fourth  to  the  eighth  dorsal  vertebra;  so  that  there 
cannot  be  much  movement  between  the  bones.  In  the  loins,  the  thick- 
ness of  the  intervertebral  substances,  the  horizontal  and  wide-apart  spines, 
and  the  shape  of  the  articular  processes  combined,  allow  more  motion  than 
in  the  back,  but  less  than  in  the  neck. 

The  movements  of  which  the  spine  is  capable  are  threefold:  (1)  Flexion 
and  extension;  (2)  Lateral  inclination;  (3)  Torsion.  Flexion  and  exten- 
sion are  freest  between  the  third  and  sixth  cervical  vertebras,  owing  to 
their  short  and  horizontal  spines;  between  the  eleventh  dorsal  and  second 
lumbar;  and,  again,  between  the  last  lumbar  and  the  sacrum.  This  is 
well  seen  in  cases  of  tetanus  ('  opisthotonos '),  where  the  body  is  supported 
on  the  back  of  the  head  and  the  heels;  or  when  a  mountebank  bends  back- 
ward and  touches  the  ground  with  his  head.  The  lateral  movement  is 
freest  in  the  neck  and  in  the  loins.  The  articulations  of  the  lumbar  ver- 
tebras admit  of  a  certain  amount  of  rotation  or  torsion,  as  proved  by  the 
following  experiment:  Sit  upright  with  your  head  and  shoulders  well  ap- 
plied against  the  back  of  a  chair;  the  head  and  neck  can  be  rotated  to  the 
extent  of  70°.  Lean  forward  so  as  to  let  the  lumbar  vertebras  come  into 
play;  you  can  then  turn  your  head  and  neck  30°  more. 

Intervertebral  Fibro-Cartilage. — The  intervertebral  fibro-cartilage 
provides  for  the  elasticity  as  well  as  the  flexibility  of  the  spine.  The 
solidity  of  this  substance  gradually  diminishes  from  the  circumference 
toward  the  centre,  where  it  forms  a  soft  and  almost  incompressible  pulp, 
permitting,  to  a  limited  extent,  the  motions  of  a  ball-and-socket  joint; 
namely,  a  gentle  bend  in  every  direction,  with  a  small  amount  of  rotation. 
Its  great  elasticity  breaks  the  force  of  jars  by  gradually  yielding,  and  always 


128  HUMAN    OSTEOLOGY. 

tends  to  restore  the  column  to  its  erect  form.  Long-continued  pressure 
during  the  day  will,  indeed,  make  the  intervertebral  substances  yield,  so 
that  a  man  loses  in  height  perhaps  £  or  even  |  an  inch;  but  this  is  recov- 
ered after  a  night's  rest.  At  the  same  time  it  should  be  remembered, 
that  a  habit  of  leaning  too  much  on  one  side  will  make  the  yielding  of 
the  intervertebral  substance  permanent.  Even  the  bones  themselves, 
while  they  are  growing,  will  yield  under  such  circumstances.  There  may 
be  considerable  distortion  without  actual  disease. 

Shape  of  the  Column  from  the  Front. — As  to  the  form  of  the 
column  in  front,  we  observe  that  it  is  pyramidal,  and  that  the  bodies  of 
the  vertebrae  gradually  increase  in  size  from  above,  and  form  a  broader 
and  broader  base  of  support  as  the  weight  to  be  supported  by  each  one 
in  succession  becomes  greater.  The  atlas,  in  consequence  of  the  great 
projection  of  its  transverse  processes,  necessary  for  the  rotation  of  the 
head,  tops  the  pillar  like  a  '  capital/  It  is,  however,  necessary  to  remark, 
that  there  is  a  partial  enlargement  of  the  column  about  the  lower  part 
of  the  cervical  region,  which  gives  a  broader  base  to  the  neck;  and  again 
a  slight  decrease  in  its  breadth,  about  the  third  and  fourth  dorsal  verte- 
brae, which  allows  more  room  for  the  lungs.  Moreover,  we  commonly 
observe  a  very  gentle  lateral  curve  in  the  dorsal  region,  particularly  about 
the  third,  fourth,  and  fifth  vertebrae,  with  the  concavity  toward  the  left 
side.  The  cause  of  this  curve  has  been  much  discussed.  Some  anatomists 
attribute  it  to  the  more  frequent  use  of  the  right  arm;  others  to  the 
presence  of  the  aorta.  The  solution  of  the  question  is  of  no  practical 
value;  all  we  need  remember  is,  that  the  curve  is  natural. 

Back  of  the  Column. — At  the  back  of  the  column,  we  observe  the 
long  row  of  spinus  processes  forming  the  vertical  crest  which  gives  the  name 
to  the  'spine/  The  spines  of  the  vertebrae  should  be  examined  on  the 
living  subject  when  the  head  is  bent  forward  and  the  arms  folded.  At 
the  risk  of  repetition  we  will  again  direct  attention:  1.  To  the  suppres- 
sion of  the  spine  in  the  atlas,  which  permits  the  free  extension  of  the 
head.  2.  To  the  great  projection  and  bifurcation  of  the  spine  of  the  axis 
which  gives  attachment  to  the  inferior  oblique  muscles  which  rotate  the 
head  and  atlas.  3.  To  the  shortness  and  horizontal  position  of  the  spines 
of  the  third,  fourth,  and  fifth,  which  allows  of  free  extension.  4.  To  the 
spine  of  the  '  vertebra  prominens/  where  the  ligamentum  nuchse  is 
attached.  5.  To  the  overlapping  of  the  long  spines  of  the  dorsal  vertebrae 
which  limits  movement  in  the  region  of  the  heart  and  lungs.  These 


PLATE  XXVII. 


THE    VERTEBRAL    COLUMN.  129 

organs  could  not  resist  stretching  or  compression  like  the  abdominal 
viscera.  G.  To  the  square  lumbar  spines,  the  planes  of  which  are  vertical 

Vertebral  Groove. — On  either  side  of  the  spine  is  a  deep  furrow, 
termed  the  '  vertebral  groove/  and  formed  by  the  laminae.  It  is  bounded 
in  the  neck  and  back  by  the  transverse  processes,  in  the  loins  by  the  articu- 
lar processes.  The  groove  is  narrowest  about  the  junction  between  the 
last  dorsal  and  first  lumbar  vertebras  (the  weakest  part  of  the  back),  and 
widest  at  the  sacrum.  The  groove  is  occupied  by  the  strong  muscles  of 
the  back.  The  crest,  being  all  that  we  can  either  see  or  feel  of  the  spine 
during  life,  is  the  part  we  immediately  examine  in  cases  of  injury  or  dis- 
ease. In  making  this  examination,  we  ought  to  be  aware  that  the  spines 
of  the  several  vertebrae  do  not  always  succeed  each  other  in  a  precisely 
straight  line,  but  that  one,  here  and  there,  may  deviate  to  the  right  or 
the  left,  even  in  persons  of  the  strongest  frame. 

Throughout  the  spine  the  intervertebral  foramina  are  in  front  of  the 
articular  processes.  But  it  is  worth  observing  that  the  transverse  pro- 
cesses vary  in  position.  In  the  cervical  region  they  lie  between  the  foram- 
ina and  are  grooved  by  nerves.  In  the  dorsal  region  they  lie  further 
back  between  the  articular  processes  in  accommodation  to  the  ribs  which 
lie  between  the  foramina.  In  the  lumbar  region  the  transverse  processes 
lie  between  the  articular  processes  and  the  intervertebral  foramina. 

Vertebral  Canal. — Respecting  the  vertebral  canal  (shown  through- 
out in  Plate  XXVII.),  remark  how  well  it  is  protected  from  injury  by  the 
breadth  of  the  arches  of  the  vertebrae.  The  arches  overlap  each  other, 
so  that  it  would  be  difficult  for  a  cutting  instrument  to  penetrate  any- 
where, except  perhaps  in  the  lumbar  region,  and,  again,  between  the  arch 
of  the  atlas  and  the  occiput,  where  animals  are  usually  '  pithed/  The 
area  of  the  canal  is  larger  in  the  lower  cervical  and  in  the  lumbar  region 
than  elsewhere,  for  the  reason  that  the  spinal  cord  itself  presents  corre- 
sponding enlargements  in  those  parts  where  the  great  nerves  of  the  limbs 
proceed  from  it.  Observe  well  the  relative  size  and  mode  of  formation  of 
the  intervertebral  foramina  by  the  notches  (Nor.  Hum.  Ost.  No.  73). 

Ossification. — As  a  rule,  each  vertebra  is  ossified  in  cartilage  from 
eight  centres,  of  which  three  are  '  principal/ — namely,  one  for  the  body 
and  one  on  each  side  for  the  arch  and  its  processes  (Nor.  Hum.  Ost.  No. 
35):  the  remaining  five  are  'epiphyses/  and  appear,  soon  after  the  age  of 
puberty,  as  follows: — one  in  the  cartilaginous  end  of  the  spinous  process, 

one  in  the  cartilaginous  end  of  each  of  the  transverse  processes,  and  one 
9 


130  HUMAN    OSTEOLOGY. 

for  each  of  the  discs  which  form  the  articular  surfaces  of  the  body.  The 
five  epiphyses  become  united  to  the  vertebra  by  bone  about  the  twenty- 
fifth  year. 

Ossification  usually  commences  at  the  sides  of  the  arch  just  before  it 
begins  in  the  body  of  the  vertebra, — viz.  about  the  seventh  week  after 
conception.  The  sides  of  the  arch  unite  first  at  the  base  of  the  spinous 
process,  so  that  the  ossification  of  the  arch  is  complete  in  the  first  year 
after  birth.  During  the  third  year  the  bases  of  the  arch  unite  with  the 
independently  ossified  ' centre'  or  ' body/ 

It  must  be  borne  in  mind  that  the  sides  of  the  bodies  are  ossified  from 
the  arches;  the  line  of  junction  is  the  '  neuro-central  suture '  of  scientific 
anatomists. 

Exceptions  to  the  General  Rule. — Where  vertebrae  undergo  great 
modifications  of  form,  we  meet  with  exceptions  to  the  above  rule.  Thus 
the  atlas  has  only  two  '  primary '  centres, — one  for  each  of  its  lateral  halves; 
and  two  '  epiphyses/  one  for  the  anterior  tubercle,  the  other  for  the  pos- 
terior. The  odontoid  process  of  the  axis  has  two  additional  centres  placed 
side  by  side  and  unites  to  the  body  in  the  third  year.  It  has  also  two 
small  epiphyses,  one  at  the  tip,  and  another  between  the  centres  for  the 
process  and  the  centre  for  the  body  of  the  axis.  These  epiphyses  are 
homologues  of  the  discs  of  ordinary  vertebrae,  and  help  to  justify  the 
general  opinion  that  the  odontoid  process  is  really  the  body  of  the  atlas; 
although,  if  it  be  BO,  it  is  remarkable  that  this  body  should  have  a  pair 
of  centres. 

There  is  a  separate  ossification  for  the  '  superior  tubercles '  or  '  mammil- 
lary  processes'  of  the  lumbar  vertebras. 

Comparative  Osteology. — In  all  known  mammalia  there  are  seven 
cervical  vertebrae,  with  the  following  exceptions:  Hoffman's  two-toed  sloth 
— Cholospus  Hoffmannii  (No.  2387  F)  has  six;  the  Three-toed  sloth— 
Bradypus  Tridactylus  (No.  2367)  has  nine.  In  Bradypus,  however,  the 
ninth,  and  sometimes  the  eighth,  bears  a  pair  of  short  movable  ribs;  the 
manatee,  again — Manatus  Americanus  (No.  2647  a) — has  only  six  cervical 
vertebras.  The  number  of  cervical  vertebras  bears  in  no  case  any  relation 
to  the  length  of  the  neck.  The  short  neck  of  the  whale  and  the  long 
neck  of  the  giraffe  (No.  3617)  contain  each  seven  cervical  vertebras.  The 
Greenland  fin- whale  in  the  Mus.  Roy.  Coll.  Surg.,  appears  to  have  but  one 
cervical  vertebra.  An  inspection  of  the  transverse  processes,  however, 
shows  that  it  has  seven,  and  that  they  have  become  anchylosed.  The 


THE   VEBTEBEAL    COLUMN.  131 

lesser  fin-whale,  next  to  it,  has  the  seven  vertebral  bodies  perfectly  dis- 
tinct. 

The  bifurcation  of  the  spines  of  the  cervical  vertebrae  is  almost  peculiar 
to  the  human  skeleton.  It  affords  more  room  for  the  insertion  of  the 
powerful  muscles  which  maintain  the  neck,  and  therefore  the  head,  erect. 

In  the  gorilla,  the  spines  of  the  five  lower  cervical  vertebras  (No.  5178) 
are  longer  in  proportion  than  those  of  any  other  known  animal.  They 
measure  from  three  to  four  inches  in  length,  and  form  one  of  the  most 
striking  features  of  difference  between  this  skeleton  and  that  of  man. 

The  whale  (Cetacea)  has  no  odontoid  process,  and  thus  differs  from 
the  manatee  (Sirenia),  which  has  a  well-marked  one.  See  Series  of  Sepa- 
rate Bones,  Mus.  Koy.  Coll.  Surg. 

In  the  chameleon  each  of  the  two  lower  cervical  vertebras  bears  a  pair 
of  cervical  ribs  (Nos.  664  a,  665  a);  and  in  the  snakes  all  the  vertebra, 
excepting  those  of  the  tail,  carry  movable  ribs.  Cervical  ribs  may  also 
be  seen  in  crocodiles  (see  Nilotic  Crocodile,  No.  717  D). 

When  mammalian  vertebras  are  very  numerous,  the  great  number  is 
made  up  of  caudal  vertebras;  but  when  a  bird's  vertebrae  are  numerous, 
the  number  is  made  up  of  cervical.  There  are  nine  in  the  neck  of  the 
sparrow,  and  twenty-three  in  that  of  the  swan. 

In  the  wading  birds  (Grallatores),  whose  long  legs  raise  the  body  some 
two  feet  or  more  above  the  water  in  which  -they  wade,  the  neck  is  long 
enough  to  enable  their  beaks  to  reach  the  ground.  Thus  their  necks  are 
in  proportion  to  the  length  of  their  legs.  See  the  flamingo. 

In  swimming  birds,  as  ducks  and  swans,  the  length  of  the  neck  is  in 
no  relation  to  the  length  of  their  short  legs,  but  is  in  proportion  to  the 
depth  to  which  they  have  to  reach  for  food. 

In  man  the  upper  and  lower  surfaces  of  the  bodies  of  the  vertebras  are 
slightly  cup-shaped,  and  receive  in  their  depressions  the  convex  surfaces 
of  the  discs  of  fibro-cartilage,  which  are  placed  between  the  bodies  of  the 
vertebra?,  and  give  the  spinal  column  its  elasticity.  In  most  fishes  the 
bodies  are  so  deeply  cupped  above  and  below,  that  there  is  a  perforation 
in  the  centre  through  which  the  intervertebral  substances  are  continuous 
(Nos.  433  to  437).  In  man  the  soft  central  part  of  this  intervertebral 
substance  is  the  remains  of  the  chorda  dorsalis,  which  persists  in  fishes, 
and  is  continuous  through  the  central  perforations.  See  the  central  cavi- 
ties for  the  chorda  dorsalis  in  the  blue  shark,  No.  413;  also  No.  13.  In  the 
mud  fish  (Dipnoi)  all  the  notocord  is  persistent,  and  there  are  no  centra 


132  HUMAN    OSTEOLOGY. 

to  the  vertebrae  whatever.  This  may  also  be  seen  in  the  Amphioxus 
Lanceolatus  (No.  8). 

The  epiphyses  on  the  upper  and  lower  surfaces  of  the  bodies  of  the 
vertebrae  should  be  especially  examined  in  the  whale  (Separate  Series). 
They  form  complete  plates  of  great  size,  and  being  separable  from  the 
bodies  of  the  vertebrae  in  many  of  these  animals,  are  very  abundant  on 
the  sea-shore  in  northern  climates.  It  is  interesting  that  when  H.M.S. 
'  Hecla '  was  wrecked,  the  crew  used  these  discs  as  plates. 

In  serpents  (Ophidia)  the  body  of  each  vertebra  is  cup-shaped  in  front, 
and  receives  the  rounded  head  of  the  one  in  front  of  it  (Nos.  604  to  609), 
and  this  is  the  same  in  many  of  those  of  the  crocodiles  in  which  the  upper 
surfaces  of  the  bodies  are  cup-shaped,  and  each  receives  the  convex  pro- 
jection from  the  lower  surface  of  the  vertebra  above. 

In  many  flying  birds,  the  dorsal  vertebrae  are  fixed  to  one  another  by 
fusion  of  the  spines,  and  often  of  the  transverse  processes  and  bodies.  In 
birds  that  do  not  fly,  such  as  the  cassowary  and  the  ostrich,  they  retain 
their  mobility  (Nos.  1633,  1633  A— B  and  1634). 

The  vertebras,  which  vary  in  number  so  widely  throughout  the  animal 
kingdom,  attain  in  the  tiger  boa  (Python  tigris,  No.  602)  the  enormous 
number  of  291  in  all. 

In  tortoises  (Chelonia)  the  dorsal  vertebrae  are  immovably  connected, 
and  have  no  transverse  processes.  The  proximal  ends  of  the  ribs  unite 
directly  with  the  vertebrae,  and  are  also  immovable. 


THE   SAOEUM. 

(PLATES  XXVIII.,  XXIX.) 

Situation  and  Inclination.  —  The  'sacrum'76  is  situated  at  the  back 
of  the  pelvis,  and  wedged  in  between  the  two  innominate  bones.     It 


75  It  is  not  easy  to  say  why  this  was  called  the  '  sacred  bone  '  ({epov 
The  reason  generally  assigned  is,  that  it  was  the  part  used  in  sacrifices.    The  following 
is  another:  —  It  appears  the  Jewish  Rabbis  entertained  a  notion  that  this  part  of  the 
skeleton,  which  they  call  the  '  luz,'  would  resist  decay,  and  become  the  germ  from 
which  the  body  would  be  raised.     Hence  Butler  has  it— 
'  The  learned  Rabbins  of  the  Jews,  • 
Write  there's  a  bone,  which  they  call  "  Luz," 
I'  the  rump  of  man,  of  such  a  virtue, 
No  force  in  nature  can  do  hurt  to  : 


PLATE  XX.V1II. 


SACRUM. 

Promontory. 


Gltrteus  rna.* 


TermmationoP  Vertebral  ta.nal...- 


Koteh  fbr  fifth  sacral  nerve. 

Cornu, 


Posterior  view, 


coccy  x 


THE     SACRUM.  133 

forms  the  '  keystone '  of  the  arch  which  supports  the  spine,  and  transmits 
the  weight  of  it  to  the  lower  limbs.  Observe  that  it  inclines  backward, 
and  forms,  with  the  last  lumbar  vertebra,  a  rounded  angle,  termed  the 
'  promontory '  of  the  sacrum.  This  inclination  answers  a  double  purpose: 
it  not  only  makes  the  pelvis  capacious,  but  breaks  the  force  of  shocks 
transmitted  from  the  pelvis  to  the  spine. 

Composed  of  five  Vertebrae. — Its  general  shape  is  triangular.  It 
plainly  consists  of  five  vertebrae,"  with  their  bodies  and  processes  all  con- 
solidated into  a  single  bone.  Examine  its  anterior  and  posterior  surfaces, 
its  sides,  its  base,  and  its  apex. 

Anterior  Surface. — Its  anterior  surface  is  concave  from  above 
downward,  and  from  side  to  side,  in  adaptation  to  the  pelvic  cavity. 
The  curvature  of  the  bone  forward,  inferiorly,  not  only  assists  in  sup- 
porting the  pelvic  viscera,  but  permits  us  to  sit,  which  we  could  not  have 
done  had  the  bone  projected  like  a  tail.  In  the  middle,  are  the  anchy- 
losed  bodies  of  the  five  sacral  vertebras  decreasing  in  size  from  above 
downward,  and  the  four  transverse  ridges  indicating  their  union.  On 
each  side  of  the  ridges  are  the  four  anterior  sacral  foramina,  with  grooves 
leading  from  them  for  the  passage  of  the  anterior  branches  of  the  sacral 
nerves. 

The  bone  exterior  to  the  foramina,  on  each  side,  is  made  up  of  parts 
which  in  the  three  upper  sacral  vertebrae  are  homologous  to  ribs.  These 
are  united  to  the  bodies,  to  each  other,  and  to  the  transverse  processes 
behind,  so  as  to  form  a  solid  lateral  mass.  Here  the  '  pyriformis '  arises. 
(Plate  XLVII.) 

Posterior  Surface. — The  posterior  surface  of  the  sacrum  is  convex, 
and  presents,  in  the  middle  line,  the  spines  of  the  four  upper  sacral  ver- 
tebrae, usually  coalesced  into  a  vertical  crest,  for  the  origin  of  the  'erector 


Therefore  at  the  last  great  day, 

All  th'  other  members  shall,  they  say, 

Spring  out  of  this,  as  from  a  seed 

All  sorts  of  vegetals  proceed; 

From  whence  the  learned  sons  of  art 

"Os  sacrum"  justly  call  that  part.' 

HUDIBRAS,  part  iii.  cant.  ii. 

76  It  is  not  uncommon  to  meet  with  six  sacral  vertebra;.  Sometimes  there  are  but 
four.  The  first  sacral  may  be  detached  from  the  lower  sacral  vertebrae.  Again,  the 
last  lumbar  may  be  anchylosed  to  the  sacrum  by  its  body,  or  to  the  ilium  by  one  or 
both  of  its  transverse  processes.  This  last  condition  is  frequent  among  the  higher 
monkeys. 


134  HUMAN    OSTEOLOGY. 

spinse.'  The  last  sacral  vertebra,  and  sometimes  the  last  two,  have  no 
spines,  and  even  their  arches  are  more  or  less  deficient,  so  that  the  ter- 
mination of  the  vertebral  canal  is  here  left  unprotected  in  the  dry  bone: 
and  in  the  recent  state  it  is  covered  only  by  a  fibrous  membrane.  This 
explains  the  serious  effects  that  are  apt  to  follow  an  injury  to  this  part. 
Sloughs  from  bed-sores  are  sometimes  deep  enough  to  expose  the  ver- 
tebral canal.  On  each  side  of  the  crest  is  the  vertebral  groove;  and  here 
are  the  faint  traces  of  the  anchylosed  articular  processes  of  the  sacral  ver- 
tebrae. The  most  conspicuous  of  these  processes  are  those  of  the  last 
vertebra:  they  project  like  two  knobs  of  bone,  and  are  called  the  '  cornua' 
of  the  sacrum:  they  correspond  with  the  cornua  of  the  coccyx,  with 
which  they  are  connected  by  ligaments. 

Posterior  Foramina  and  Tubercles. — Next  to  the  articular  pro- 
cesses are  the  four  foramina  which  transmit  the  posterior  sacral  nerves. 
These  posterior  foramina  are  directly  opposite  the  anterior.  Beclard, 
in  his  lectures,  relates  the  case  of  a  sharp  instrument  running  through 
both  into  the  pelvic  cavity.  The  fifth  sacral  nerve  emerges  through 
the  little  '  notch '  beneath  the  sacral  cornu.  Still  more  externally  are 
the  '  tubercles/  indicating  the  anchylosed  transverse  processes.  These, 
like  the  crest,  give  origin  to  the  tendon  of  the  '  erector  spinae.'  (Plate 
XLIII.) 

Base  of  Sacrum.— The  base  or  upper  end  of  the  sacrum  presents 
the  oval  surface  of  the  body  of  the  first  sacral  vertebra,  which  artic- 
ulates with  the  last  lumbar,  a  thick  fibro-cartilage  intervening.  "When 
the  bone  is  in  its  proper  position,  this  upper  surface  slants  downward 
and  forward,  forming,  with  the  lumbar  vertebra,  the  sacro-vertebral 
angle,  or  '  promontory/  before  referred  to  (page  133).  On  each  side  of 
the  body  are  its  thick  and  strong  lateral  masses  expanded  like  wings, 
which  transmit  the  weight  of  the  trunk  to  the  iliac  bones.  Each  Aving 
has  a  rounded  edge  in  front,  which  forms  part  of  the  brim  of  the  true 
pelvis.  Behind  the  body  is  the  triangular  opening  of  the  vertebral  canal 
formed  by  the  vertebral  arches.  Lastly,  on  each  side  of  the  canal  are 
the  articular  processes  for  the  last  lumbar  vertebra.  They  are  set  very 
wide  apart,  giving  a  broad 'base  of  support  to  the  spine;  they  look  back- 
ward and  inward,  are  slightly  concave  from  side  to  side,  and  thus  per- 
mit a  slight  rotatory  movement.  In  front  of  each  articular  process  is 
the  indication  of  the  notch  for  the  passage  of  the  last  lumbar  nerve. 

Apex. — The  apex  of  the  sacrum  is  formed  by  the  diminutive  body 


THE     SACRUM.  135 

of  the  last  sacral  vertebra,  and  has  an  oval  articular  surface  for  the 
coccyx. 

Sacro-iliac  Symphysis. — At  the  sides  of  the  sacrum,  notice  the 
surface  which  is  connected  to  the  ilium,  forming  what  is  called  the 
'  sacro-iliac '  symphysis.  Three  sacral  vertebrae  concur  to  form  it.  The 
connection  is  effected,  partly  by  cartilage,  partly  by  ligament.  The  car- 
tilaginous part  is  in  front,  and  is  mapped  out  on  the  dry  bone  in  the  shape 
of  a  little  ear,  hence  it  is  called  the  '  auricular '  surf  ace  of  the  sacrum. 
Behind  this  is  the  rough  and  deep  excavation  denoting  the  attachment  of 
the  strong  interosseous  ligament  connecting  the  two  bones.  Separation 
of  the  '  sacro-iliac '  symphysis  does  sometimes,  though  rarely,  take  place 
as  the  result  of  injury.  It  is  an  accident  of  the  gravest  kind,  and  one 
rarely  sees  recovery  in  such  a  case,  since  it  is  almost  sure  to  be  accom- 
panied with  other  injury  to  the  pelvic  viscera.  Lastly,  the  side  of  the 
sacrum  below  the  auricular  part  gives  origin  to  some  of  the  fibres  of  the 
'gluteus  maximus.' 

Ossification. — The  sacral  vertebrae  are  ossified  like  the  others,  with 
the  addition  of  an  independent  centre  on  each  side  of  the  first  three  for 
the  formation  of  the  lateral  mass.  Now,  since'  every  vertebra  has  three 
primary  centres  (one  for  the  body  and  two  for  the  laminae,  or  arches), 
and  two  secondary  centres  for  the  body  (the  discs  on  the  upper  and  lower 
surfaces),  the  number  of  centres  for  the  five  sacral  vertebras  stands  thus: 

3X5=15  centres  for  the  bodies. 
2x5  =  10  centres  for  the  arches. 
2x3=  6  additional  centres  for  the  lateral  masses  of  the  first  three 

vertebrae, 
that  is  31. 

To  these  add  four  epiphysial  plates,  two  on  each  side,  the  upper  for 
the  auricular  surface,  the  lower  for  the  outer  margin  of  the  sacrum  be- 
neath that  surface — making  in  all  35  centres. 

The  component  parts  of  each  vertebra  unite  together  first.  Thus 
complete,  the  vertebrae  remain  separate  until  about  the  15th  year,  when 
they  begin  to  unite;  not  all  at  once,  but  in  regular  succession  from  below 
upward.  The  lateral  masses  unite  before  the  bodies.  The  'auricular' 
discs  do  not  appear  till  about  the  20th  year,  and  the  whole  bone  is  not 
consolidated  before  the  26th  year,  or  thereabouts.  However,  even  in  ad- 


136  HUMAN    OSTEOLOGY. 

vanced  age,  one  sometimes  finds  the  bodies  of  the  upper  sacral  vertebrae 
still  united  in  the  centre  by  cartilage  only. 

Comparative  Osteology. — Animals  with  well-developed  hind-legs, 
which  articulate  with  a  pelvis,  have  a  more  or  less  developed  sacrum, 
formed  by  one  or  more  vertebrae.  Supple  animals,  such  as  the  tiger,  will 
be  seen  to  have  a  very  rudimentary  sacrum;  the  component  parts  are  not 
welded  together  into  a  confused  mass  like  that  of  man. 

Snakes  (Ophidia)  have  no  sacrum,  although  there  are  rudimentary 
hind  limbs  in  Typhlops,  Python  Kegius  and  Tortrix.  In  the  dugong 
and  manatee  (No.  2647,  Sirenia)  the  sacrum  is  wanting  as  well  as  the 
hind  limbs. 

There  is  no  sacrum  in  the  whales  (Cetacea). 

The  simplest  form  of  sacrum  is  seen  in  the  frog.  It  consists  of  one 
vertebra  only,  the  transverse  processes  of  which  are  expanded  to  articu- 
late with  the  ilia. 


THE  COCCYX. 

(PLATES  XXVIII.,  XXIX.) 

Constitution  and  Shape. — The  coccyx  derives  its  name  from  a 
fancied  resemblance  to  the  beak  of  a  cuckoo  (HOHHV^).  It  consists  of  four 
or  sometimes  five  rudimentary  vertebrae,  articulated  (or  anchylosed)  to- 
gether, and  successively  decreasing  in  size,  the  last  being  a  mere  nodule 
of  bone.  As  a  whole,  it  is  triangular.  The  body  of  the  first  coccygeal 
vertebra  articulates  by  an  oval  surface  with  that  of  the  last  sacral:  and 
it  has  two  little  articular  processes  termed  '  cornua '  which  are  connected 
with  the  'cornua'  of  the  sacrum,  either  by  fibrous  tissue  or  cartilage. 
The  first  vertebra  has  also  two  rudimentary  transverse  processes,  and  two 
*  notches '  (one  beneath  each  cornu)  for  the  last  sacral  nerves. 

The  first  coccygeal  vertebra  articulates  with  the  lower  end  of  the  sa- 
crum by  an  intervening  fibro- cartilage,  and  the  succeeding  ones  are  also 
separated  by  a  fibro-cartilage.  Thus  the  coccyx  admits  of  being  bent 
backward  and  forward,  which  is  of  great  advantage  in  parturition,  and 
gives  as  much  as  one  inch  more  space  in  the  antero-posterior  diameter 
of  the  outlet  of  the  pelvis.  About  the  age  of  45  or  50,  and  indeed  some- 
times earlier,  these  little  bones  become  anchylosed  to  each  other  and  to 


PLATE  XXIX. 


Articular  process  forXumbar Vertebra  . 
Vertebral  canal 


Arhcular  surface 


Tubercles  or 
Tra  ns  v  e  rse  procest 


TIU  o?  Sacrum. 
Ccrnu  of  Coccyx . 


Post  enor  surface  oP    3&crum  . 
with  muscles  CsttacTiecI. 


THE    COCCYX.  137 

the  sacrum.  This  condition  is  one  of  the  causes  of  difficult  labor,  and  is 
generally  met  with  in  women  bearing  a  first  child  late  in  life,  and  in  those 
who  have  been  accustomed  to  sit  during  the  greater  part  of  the  day,  as  in 
the  case  of  milliners. "  Under  these  circumstances,  the  bone  .will  some- 
times break  in  labor.  It  is  a  most  distressing  accident,  and  causes  great 
pain  when  the  bowels  are  acting. 

Dr.  Hunter  says  that  anchylosis  of  the  sacrum  and  coccyx  is  common 
in  females  who  ride  much  on  horseback,  and  thus  explains  the  compara- 
tive frequency  of  hard  labors  in  English  ladies.  Father  Dobritzhofer, 
who  lived  a  long  time  a  missionary  among  the  Abiponians,  speaks  of  the 
difficult  labors  of  the  women  there,  who  spend  the  greater  part  of  their 
time  on  horseback. 

Ossification.— Each  bone  of  the  coccyx  is  ossified  from  a  single  cen- 
tre. The  first  begins  to  ossify  soon  after  birth;  the  second  about  the  fifth 
year;  the  third  about  the  tenth;  and  the  fourth  about  the  fifteenth  or 
twentieth  year. 

Comparative  Osteology. — The  coccyx  in  man  corresponds  to  the 
tail  of  other  animals.  It  now  and  then  happens  that  the  end  of  the 
coccyx  projects  somewhat,  and  is  enclosed  in  a  tube  of  integument;  the 
man  is  then  said  to  have  a  tail,  and  is  looked  upon  by  the  vulgar  with 
great  suspicion. 

In  Mammalia  the  number  of  caudal  (or  coccygeal)  vertebra  mostly  far 
exceed  those  of  any  other  region.  This  may  be  seen  in  the  tail  of  the 
great  ant-eater,  which  has  forty,  and  that  of  the  long-tailed  Manis,  which 
has  forty-five.  The  Barbary  ape  (No.  4919)  has  but  three  caudal  verte- 
bra?. The  gibbon  (No.  5026)  has  two.  The  vampire  bat  (No.  2416,  g) 
is  the  only  mammalian  animal  which  has  no  coccyx. 

In  all  birds,  except  the  extinct  Archaeopteryx,  the  caudal  region  of 
the  spine  is  shorter  than  the  body,  and  numbers  only  eight  or  nine  at 
most.  In  nearly  all  birds  the  terminal  vertebrae  will  be  seen  to  be  anchy- 
losed  into  a  ploughshare-shaped  bone,  as  in  the  ostrich  and  the  vulture 
(Xo.  1674).  In  No.  70,  A  (the  sheat-fish  and  the  halibut)  the  last  caudal 
vertebra  is  triangular  and  flat,  and  to  the  posterior  edge  of  it  articulate 
the  rays  forming  the  tail. 

71  Dr.  Ramsbotham's  '  Principles  and  Practice  of  Obstetric  Medicine  and  Sur- 
gery, '  5th  edition,  p.  9. 


BONES  OF  THE  LOWER  EXTREMITY. 

Constituent  Bones. — The  bones  of  the  lower  extremity  consist  of 
the  'femur/  the  'patella/  the  two  bones  of  the  leg,  namely,  the  'tibia* 
and  '  fibula/  the  bones  of  the  '  tarsus,'  the  '  metatarsus/  and  the  '  phalanges' 
of  the  toes. 

The  femur  articulates  with  the  pelvis.  The  pelvis  consists  of  the  '  os 
sacrum/  the  coccyx,  and  the  two  '  ossa  innominata.'  These  bones  form 
an  arch,  of  which  the  sacrum  is  the  keystone,  and  the  innominate  bones 
are  the  pillars.  (Plate  XXXII.)  The  weight  of  the  spine  is  supported 
on  the  top  of  the  sacrum,  and  the  pressure  is  communicated  down  the 
pillars  of  the  arch  to  the  thigh  bones  which  articulate  with  the  innominate 
bones.  It  is  in  this  way  that  the  weight  of  the  body  is  supported  by  the 
lower  extremities. 


OS  INNOMINATUM. 

(PLATE  XXX.) 

General  Description. — The  '  os  innominatum/  so  named  by  Galen, 
is  made  up  of  three  bones,  distinct  in  childhood,  but  united  in  the  adult, 
and  termed  the  'ilium/  'ischium/  and  'pubes/  Thus  its  constituents 
have  received  appropriate  names,  but  the  bone,  consolidated,  remains 
'  nameless.'  The  '  ilium*  is  the  expanded  part  which  supports  the  flank 
(ilia) ;  the  '  ischium '  supports  the  body  in  the  sitting  posture  (  iffxi<x,  the 
buttocks);  the  '  pubes'  is  the  front  part — so  called  from  its  being  covered 
with  hair.  All  three  contribute  to  form  the  'acetabulum/  or  socket  for 
the  head  of  the  femur,  and  in  the  following  proportions  (Plate  XXX. 
Fig.  3): — the  ischium  contributes  rather  more  than  two-fifths,  the  ilium 
rather  less  than  two-fifths,  and  the  pubes  about  one-fifth.  Until  the  age 
of  puberty  they  are  separated  at  the  bottom  of  the  acetabulum  by  a  piece 
of  cartilage  shaped  like  the  letter  Y;  in  the  adult,  however,  little  trace  is 


PLATE  XXX. 


OS    ENNOMINATUM.  139 

left  of  the  original  division,  so  that,  for  practical  purposes,  it  is  better 
to  consider  the  bone  as  one,  and  to  describe  successively  its  iliac,  pubic, 
and  ischial  portions. 

In  studying  the  relative  bearings  of  these  several  parts  in  the  erect 
position  of  the  body,  it  is  necessary  that  the  bone  be  held  at  such  an  in- 
clination that  the  '  notch '  in  the  margin  of  the  acetabulum  directly  faces 
the  ground. 

Ilium. — The  'ilium'  (os  ilii)  forms  abroad  expanse  for  the  support  of 
the  abdominal  viscera,  and  gives  a  powerful  leverage  to  the  great  muscles 
which  balance  the  pelvis  on  the  head  of  the  femur.  Examine  its  outer 
and  inner  surfaces,  and  its  borders. 

Outer  Surface  of  Ilium. — The  outer  surface  of  the  ilium  (dorsum 
ilii)  is  slightly  undulating,  being  convex  on  its  anterior  half,  and  concave 
on  its  posterior.  In  a  well-marked  bone  there  are  distinct  traces,  termed 
the  '  superior  and  inferior  curved  lines/  which  map  out  the  origins  of 
the  gluteal  muscles.  These  lines  commence,  the  one  at  the  '  anterior 
superior  spine/  the  other  at  the  '  anterior  inferior  spine/  and  extend 
backward  to  the  'greater  ischiatic  notch.'  The  surface  above  the  supe- 
rior line  gives  origin  to  the  '  gluteus  medius ';  that  between  the  lines  to 
the  'gluteus  minimus.'  A  rough  surface  further  back  indicates  the  ori- 
gin of  a  part  of  the  '  gluteus  maximus.'79  Just  above  the  acetabulum  is 
one  origin  of  the  '  rectus  femoris/  the  other  being  at  the  '  anterior  infe- 
rior spine.' 

Inner  Surface :  Iliac  Fossa. — The  inner  surface  of  the  ilium  is 
slightly  excavated,  forming  the  '  iliac  fossa.'  This  fossa  is  one  of  the  char- 
acteristics of  the  human  skeleton;  it  supports  the  abdominal  viscera,  and 
gives  origin  to  the  'iliacus.'  Hold  the  bone  to  the  light,  and  observe 
that  the  bottom  of  the  fossa  is  the  thinnest  part  of  the  ilium:  it  is  out  of 
the  line  of  the  weight  of  the  body.  The  fossa  is  bounded  below  by  the 
'linea  ilio-pectinea/  which  forms  the  true  '  brim  of  the  pelvis.'  This 
brim  is  the  thickest  and  strongest  part  of  the  bone,  since  it  is  the  '  line  of 
the  pelvic  arch/  along  which  the  weight  of  the  trunk  is  transmitted  to 
the  head  of  the  thigh  bone.  No  one  can  form  an  adequate  idea  of  the 
massive  architecture  of  this  part  of  the  pelvis  without  inspecting  a  verti- 

18  The  ridge  between  the  origin  of  the  gluteus  medius  and  the  iliac  origin  of  the 
gluteus  maximus  is  called  the  '  superior  curved  line  '  by  some  anatomists;  then,  our 
'  superior'  is  their  '  middle.'  Authors  differ  about  the  names  of  these  '  lines,'  but 
agree  about  their  existence. 


140  HUMAN    OSTEOLOGY. 

cal  transverse  section  such  as  is  shown  in  Plate  XXXII.  Behind  the 
iliac  fossa  is  the  articular  surface  for  the  sacrum  (sacro-iliac  symphysis). 
The  front  part  of  this  is  shaped  like  a  little  ear,  and,  in  the  recent  state, 
crusted  with  cartilage,  which  acts  as  a  '  buffer '  to  the  joint,  while  the 
hinder  part  is  exceedingly  rocky  for  the  attachment  of  the  strong  '  inter- 
osseous  '  ligament  which  secures  it.  Lastly,  on  the  inner  surface  is  the 
foramen,  which  transmits  nutrient  blood-vessels  and  a  nerve  into  the  can- 
cellous  texture. 

Crest  and  Spines  of  Ilium. — The  upper  border  of  the  ilium  is 
termed  the  'crest/  Looking  at  it  from  above,  we  observe  that  its 
outline  is  alternately  concave  and  convex,  like  the  adjoining  figure  (26),  in 
adaptation  to  the  general  surface  of  the  ilium,  which  undulates  at  the  one 
part,  forming  the  '  iliac  fossa'  (i),  and  at  the  other  forming  what 
k  i  may  be  termed  the  '  gluteal  fossa '  (g),  which  lodges  the  mus- 
cles of  the  buttock.  The  crest  is  rough  and  broad,  and  is  spoken 
of  as  presenting  three  '  lips ' — an  '  outer/  an  '  inner,'  and  a 
*  middle ' — giving  origin  to  the  muscles  which  form  the  lateral 
walls  of  the  abdomen.  The  outer  lip  gives  origin  to  the  '  tensor 
fasciae  femorjs/  the  '  obliquus  externus  abdominis '  and  the  '  latis- 
righuiium.  simus  dorsi ';  the  middle  lip  gives  origin  to  the  '  obliquus  inter- 
nus ';  and  the  inner  lip  to  the  '  transversalis  abdominis,'  the  '  quadratus 
lumborum,'  and  a  part  of  the  '  erector  spina?.' 

Anterior  Spines. — Along  the  front  border  of  the  ilium  are  the 
*  anterior-superior '  and  '  anterior-inferior  spines,'  with  the  shallow  notch 
between  them.  The  superior  spine,  with  the  edge  of  the  notch  below, 
gives  origin  to  the  'sartorius,'  and  the  inferior  spine  to  one  head  of  the 
'  rectus.'  Below  this  spine  is  another  notch,  for  the  passage  of  the  iliacus 
and  psoas  muscles,  and  then  comes  the  '  ilio-pectineal  eminence,'  where 
the  ilium  and  pubes  join.  This  eminence  is  the  part  over  which  the 
femoral  artery  passes  into  the  thigh,  and  against  which  it  can  be  effect- 
ually compressed. 

Posterior  Spines  and  Ischiatic  Notches. — Along  the  posterior 
border  of  the  ilium  are  the  '  posterior-superior '  and  '  posterior-inferior 
spines,'  with  the  little  notch  between  them.  These  spines  are  for  the  at- 
tachment of  ligaments.  Below  the  spines  is  the  '  greater  ischiatic  notch,' 
which  transmits  the  great  vessels  and  nerves  from  the  pelvis  to  the  but- 
tock and  back  of  the  thigh.  Lower  still  is  the  'spine  of  the  iscbium,' 
and  then  the  '  lesser  ischiatic  notch.'  In  the  recent  state  the  notches  are 


PLATK  XXXI. 


Pyramidalis, 


..Conjoined 
tendon 

of 
Internal  oblique 


ramua 
of  Pubes . 


of  'IseTiurm . 


Fro-nt  view  op  bodly  of 


OS    ESTNOMINATUM. 


141 


converted  into  complete  holes  by  the  '  sacro-ischiatic  ligaments/  greater 
and  lesser  respectively,  as  shown  in  Fig.  27.  These  ligaments  answer  three 
important  purposes:  1.  They  mainly  contribute  to  the  fixation  of  the 
sacrum,  which  is  the  keystone  of  the  pelvic  arch;  2.  They  afford  an  ex- 


sacro-ischiatic  ligament. 


FIG.  27. 


tensive  surface  for  the  origin  of  the  great  muscle  of  the  buttock  (gluteus 
maximus);  3.  They  help  to  form  the  floor  of  the  pelvis,  and  support  the 
pelvic  viscera,  without  adding  much  to  the  weight  of  the  cavity.  The 
ischiatic  notches  transmit  the  following  objects: — 


The  GREATER  ISCHIATIC 
.  NOTCH  transmits 


The    LESSER   ISCHIATIC 
NOTCH  transmits 


Gluteal  vessels  and  nerve. 

Pyriformis  muscle. 

Greater  and  lesser  ischiatic  nerves. 

Ischiatic  vessels. 

Pudic  vessels  and  nerve  (out  of  pelvis). 
.  Nerve  to  obturator  internus  (out  of  pelvis), 
f  Tendon  of  the  obturator  internus. 
J  Nerve  to  obturator  internus  (into  pelvis). 
[  Pudic  vessels  and  nerve  (into  pelvis). 


Pubes,  Body,  and  Kami.— The  'pubes'  (Plate  XXXI.  Fig.  1)  is 
usually  described  as  having  a  'body 'and  two  branches:  one  of  which, 
called  the  '  horizontal  ramus/  joins  the  ilium  at  the  ilio-pectineal  emi- 
nence; the  other,  called  the  '  descending  ramus/  joins  the  ascending 
ramus  of  the  ischium.  These  terms  '  horizontal '  and  '  descending/  as 
descriptive  of  the  direction  of  the  '  rami/  are  likely  to  mislead.  They 
have  come  into  general  use  from  the  pelvis  having  been  described  as  if  it 
were  horizontal,  which  it  is  not.  Look  at  a  properly  articulated  skeleton, 


142  HUMAN   OSTEOLOGY. 

or  hold  the  pelvis  inclined  at  its  proper  angle  to  the  horizon,  and  you 
soon  see  that  the  pelvic  rami  run  in  a  direction  almost  the  reverse  of  that 
which  is  implied  by  their  names. 

The  '  horizontal  ramus '  of  the  pubes  is  somewhat  triangular.  Its  upper 
surface  gives  origin  to  the  '  pectineus,'  and  is  marked  by  the  continuation 
of  the  true  brim  of  the  pelvis,  or  '  linea  ilio-pectinea ,'  which  gives  inser- 
tion to  the  '  psoas  parvus '  when  there  is  one,  and  also  to  that  part  of  the 
'  crural  arch  '  termed  '  Gimbernat's  ligament.'  The  inner  surface  forms 
part  of  the  wall  of  the  true  pelvis,  while  its  lower  surface  bounds  the 
obturator  foramen,  and  is  grooved  for  the  passage  of  the  obturator  vessels 
and  nerve. 

Pubic  Arch. — The  '  descending  ramus '  of  the  pubes  inclines  out- 
ward and  backward,  and  forms,  with  its  fellow  of  the  opposite  side,  what 
is  called  the  "arch  of  the  pubes/  The  margin  of  the  arch  slopes  a  little 
outward,  and  has  a  groove  for  the  attachment  of  the  '  crus  penis '  in  the 
male,  or  '  crus  clitoridis '  in  the  female.  This  shelving  of  the  arch  is 
greater  in  women,  and  facilitates  the  passage  of  the  child.  Behind  the 
groove  is  the  origin  of  the  '  constrictor  nrethrae.' 

Body  and  Symphysis  of  the  Pubes. — The  'body 'of  the  pubes 
(Plate  XXXI.)  is  connected  along  a  rough  and  somewhat  oval  surface  to 
the  corresponding  part  on  the  opposite  bone.  This  union  is  termed  the 
'symphysis  pubis.'  Observe  the  bones  are  not  here  in  immediate  appo- 
sition, but  united  by  fibro-cartilage  of  at  least  -fths  of  an  inch  in  thickness 
in  front,  which  is  elastic,  like  that  between  the  bodies  of  the  vertebrae, 
and,  while  it  completes  the  pelvic  arch  below,  serves  also  to  obviate  the 
effects  of  concussion.  The  summit  of  the  pubes  is  a  most  important  part 
in  relation  to  the  anatomy  of  hernia.  The  chief  point  of  interest  here  is 
the  'spine.'  This  is  for  the  attachment  of  the  'crural  arch'  (Poupart's 
ligament),  and  is,  surgically,  of  great  importance  as  the  guide  to  the  ex- 
ternal abdominal  and  femoral  rings.  From  the  spine  we  trace  outward 
the  beginning  of  the  'linea  ilio-pectinea,'  where  '  Gimbernat's  ligament' 
is  attached.  Between  the  spine  and  the  symphysis  is  the  part  called  the 
'  crest,'  with  which  so  many  muscles  are  connected.  These  are,  proceeding 
from  the  front,  the  insertion  of  the  conjoined  tendon  of  the  'internal 
oblique '  and  '  transversalis,'  the  origin  of  the  '  pyramidalis,'  and  that  of 
the  '  rectus  abdominus.'  The  posterior  surface  of  the  body  forms  part  of 
the  wall  of  the  pelvic  cavity;  its  angle  of  inclination,  as  well  as  that  of 
the  '  symphysis,'  is  such  as  to  present  (in  the  erect  position)  a  gently 


OS    INNOMINATUM.  143 

sloping  plane  for  the  support  of  the  pelvic  viscera.  Lastly,  its  anterior 
surface  is  rough  for  the  origin  of  muscles:  viz.  the  '  adductor  longus,'  the 
'  adductor  brevis,'  and  part  of  the  '  adductor  magnus,'  also  the  '  obturator 
externus '  and  the  '  gracilis.' 

Ischium. — The  ischium  completes  the  lower  part  of  the  innominate 
bone.  (Plate  XXX.)  It  supports  the  trunk  in  sitting,  and  projects  for 
the  origin  of  the  hamstring  muscles.  Kegarded  separately  for  purposes 
of  description,  it  is  formed  of  a  '  body,'  which  is  the  most  bulky  part  of 
it,  for  the  formation  of  the  acetabulum:  from  this,  the  bone  drops  verti- 
cally to  form  the  '  tuberosity '  upon  which  we  sit;  and  then,  curving 
forward  like  a  hook,  it  forms  the  '  ascending  ramus,'  which  unites  with 
the  corresponding  part  of  the  pubes,  and  thus  completes  the  '  foramen 
ovale.'  'Leaving  the  acetabulum  for  separate  study,  notice  the  'spine  of 
the  ischium,'  which  separates  the  ' greater '  from  the  'lesser  ischiatic 
notch.'  Its  outer  side  gives  origin  to  the  'gemellus  superior';  its  inner 
surface  to  the  '  coccygeus '  and  a  part  of  the  '  levator  ani ' :  the  front  part 
of  the  '  levator  ani,'  observe,  arises  from  the  body  of  the  pubes,  while  the 
intermediate  part  arises  from  a  tendinous  arch  thrown  across  from  one 
point  of  bone  to  the  other.  Attached  to  the  spine  is  the  lesser  sacro- 
ischiatic  ligament;  the  internal  pudic  artery  crosses  over  its  outer  surface. 
In  case  of  severe  haemorrhage  after  lithotomy,  it  would  be  possible  in  a 
thin  subject  to  compress  the  artery  against  the  bone. 

Foramen  Ovale,  or  Obturatum.  — The  '  foramen  ovale,'  or  '  ob- 
turatum,'  is  a  wide  opening  of  an  oval  form  in  the  male,  but  triangular, 
with  rounded  angles,  in  the  female.  It  is  closed  in  the  recent  state  by 
the  *  obturator  membrane,'  everywhere  except  at  the  top,  where  there  is 
a  small  aperture  for  the  passage  of  the  obturator  vessels  and  nerve  into  the 
thigh.  The  membrane  serves  for  the  origin  of  the  obturator  muscles 
just  as  well  as  if  it  had  been  a  plate  of  bone:  besides  which,  it  gives  a 
little  during  the  passage  of  the  head  of  the  child:  it  also  materially 
lightens  the  pelvis.  Externally,  the  border  of  the  hole  gives  origin  to 
the  '  obturator  externus.'  Between  the  lips  of  the  acetabulum  and  the 
upper  part  of  the  tuberosity  is  a  groove,  in  front  of  which  the  obturator 
externus  passes  to  its  insertion  into  the  femur. 

Behind  the  foramen  ovale  (Plate  XXX.),  the  ischium  presents  a 
smooth  and  extensive  surface  which,  with  the  corresponding  part  of  the 
ilium,  forms  much  of  the  lateral  wall  of  the  pelvic  cavity.  Observe  that 
this  surface  inclines  so  as  to  form  a  gentle  slope  toward  the  lower  opening 


144 


HUMAN    OSTEOLOGY. 


of  the  pelvis.  Now  it  is  this  '  slope  of  the  ischium '  which  guides  the  head 
of  the  child  after  it  has  entered  the  brim  of  the  pelvis,  and  makes  it  turn 
so  that  the  longest  diameter  of  the  head  corresponds  with  the  widest  part 
of  the  outlet.  The  greater  part  of  the  slope  gives  origin  to  the  '  obturator 
internus/  which  also  arises  from  the  margin  of  the  obturator  foramen,  as 
well  as  the  membrane  closing  it;  and  with  this  muscle  we  associate  the 
lesser  ischiatic  notch,  because  it  forms  the  pulley  (crusted  in  the  recent 
state  with  cartilage)  round  which  the  four  tendons  of  this  muscle  turn, 
in  order  to  reach  the  thigh  bone. 

Tuberosity  of  the  Ischium. — The  tuberosity  of  the  ischium  an- 
swers a  double  purpose — 1.  It  serves  to  support  the  trunk  in  the  sitting 
position;  2.  It  forms  a  lever  for  the  action  of  the  hamstring  muscles,  of 
which  one  important  function  is  to  restore  the  body 
to  the  erect  position  after  stooping,  as  seen  in  the 
annexed  Fig.,  28.  Here  we  have  a  lever  of  the 
first  order.  The  fulcrum  F  is  at  the  hip  joint; 
the  weight  W  is  the  trunk  of  the  body;  and  the 
power  P  is  at  the  tuberosity  of  the  ischium,  where 
the  hamstring  muscles  arise.  On  the  '  tuberosity ' 
itself  are  the  rough  impressions  made  by  the  strong 
muscles  attached  to  it.  (Plate  XXX.)  Its  well- 
marked  outer  border  gives  origin  to  the  '  quad- 
ratus  femoris';  behind  this  margin  is  a  slightly 
concave  surface,  narrowest  below,  for  the  origin 
of  the  'semi-membranosus';  more  internally,  and 
separated  by  a  ridge  from  the  attachment  of  the 
last-named  muscle,  is  an  almost  plane  surface, 
FIG.  as.— The  Tuberosity  of  f rom  which  arise,  together,  the  '  semitendinosus  * 

the  Ischium,  a  Lever  of  the 

and  '  biceps/  The  '  gemellus  inferior '  arises  from 

its  upper  border.  At  its  lower  part,  anteriorly,  begins  the  origin  of  the 
'  adductor  magnus/  which  is  continued  a  long  way  up  the  ramus,  nearly 
to  the  body  of  the  pubes.  Along  the  inner  side  of  the  tuberosity  is  a 
rough  ridge  to  which  the  greater  sacro-ischiatic  ligament  is  attached:  an- 
terior to  this,  but  in  the  same  line,  is  the  origin  of  the  '  erector  penis/ 
and  that  of  the  '  transversalis  perinei  superficialis.' 

The  pudic  vessels  and  nerves  run  along  the  inner  side  of  the  ischium, 
not  quite  one  inch  and  a  half  from  the  inner  margin  of  the  tuberosity. 

Acetabulum.     Its  Direction.     Notches. — Lastly,  we  come  to  the 


OS    HTNOMINATUM.  145 

'  acetabulum/  so  named  from  its  resemblance  to  an  ancient  vinegar  cup. 
Its  great  depth  and  hemispherical  form  securely  lodge  the  head  of  the 
femur,  and  yet  allow  more  or  less  movement  in  any  direction.  It  looks 
doivnward  and  outward  (in  the  erect  position)  transmitting  the  weight  of 
the  trunk  directly  on  to  the  head  of  the  thigh  bone;  the  upper  or  iliac 
portion  of  it  has  to  support  the  whole  weight  of  the  trunk,  and  is  by  far 
the  thickest  and  strongest  part.  As  before  stated  (p.  138)  it  is  formed 
partly  by  the  ischium  (more  than  two-fifths),  partly  by  the  ilium  (less 
than  two-fifths),  and  the  remainder  by  the  pubes.  There  are  two  notches 
in  the  margin  or  '  brim '  of  the  acetabulum.  The  upper  and  smaller  one 
is  near  the  ilio-pectineal  eminence,  and  permits  the  free  bending  of  the 
thigh  toward  the  abdomen.  The  other  and  larger,  specially  called  '  the 
notch/  is  at  the  lowest  part  of  the  margin.  It  permits  the  *  adduction ' 
of  the  thigh,  as  when  we  cross  the  legs,  and  also  lets  blood-vessels  run 
into  the  acetabulum  to  supply  the  ligamentum  teres,  and  the  fat  at  the 
bottom  of  it.  Besides  which,  there  is  no  need  of  bone  at  the  lowest  part 
of  the  socket,  which  never  has  to  support  weight.  Two  ligaments  are 
attached  to  the  borders  of  the  notch:  one  is  the  ' ligamentum  teres';  the 
other  is  the  *  transverse  ligament '  which  runs  across  it  to  complete  the 
margin  of  the  acetabulum.  The  transverse  ligament  is  sometimes  ossified 
in  extreme  old  age.  (See  Nor.  Hum.  Ost.,  No.  733.)  Deep  as  it  is,  even 
in  the  dry  bone,  the  acetabulum  is  made  still  deeper  in  the  recent  state 
by  a  broad  rim  of  fibro-cartilage,  called  the  '  cotyloid  ligament/  which, 
besides  increasing  its  depth,  serves  as  a  *  sucker '  to  keep  the  head  of  the 
bone  in  the  socket. 

Excavation  at  Bottom  of  Acetabulum. — The  socket  is  smooth 
everywhere  (in  the  recent  state  crusted  with  cartilage),  except  at  the  bot- 
tom, where  there  is  an  irregular  excavation  continuous  with  the  notch 
below.  This  allows  the  free  play  of  the  ligamentum  teres  within  the 
joint;  it  is  partly  occupied  by  fat  and  synovial  fringes.  If  the  socket  be 
held  to  the  light,  the  bottom  of  it  will  be  found  translucent.  This  thin- 
ness explains  why,  in  some  cases  of  hip-joint  disease,  the  matter  makes 
its  way  through  the  socket  into  the  pelvic  cavity.  (See  St.  Barthol- 
omew's Hospital  Mus.,  Diseases  of  Joints,  No.  601.)  It  likewise  ex- 
plains why  a  fall  on  the  trochanter  major  is  able  to  fracture  the  bottom 
of  the  acetabulum.  There  is  a  preparation  (Injuries  of  Bones  and 
Joints,  Nos.  936,  937)  in  St.  Bartholomew's  Hospital  Mus.  in  which  a 

fracture,  caused  by  a  fall  on  the  trochanter  a  few  months  before  death, 
10 


146  HUMAN    OSTEOLOGY. 

extended  in  several  directions  from  the  centre  of  the  acetabulum  to  its 
circumference. 

Ossification.  —  Besides  the  three  pieces  of  which  it  is  originally 
formed,  the  os  innominatum  has  four  '  epiphyses/  which  begin  to  appear 
about  the  age  of  puberty.  One,  the  marginal  epiphysis,  skirts  the  crest 
of  the  ilium.  There  is  a  second  for  the  anterior-inferior  spine;  a  third 
along  the  tuberosity  of  the  ischium;  and  a  fourth,  which  forms  a  thin 
plate,  at  the  symphysis  pubis.  (See  Nor.  Hum.  Ost.,  Nos.  64,  65.)  The 
Y-shaped  cartilage  at  the  bottom  of  the  acetabulum  begins  to  ossify  at 
puberty.  The  ilium  begins  to  ossify  at  the  end  of  the  second  month;  the 
ischium  at  the  end  of  the  third;  and  the  pubes  at  the  end  of  the  fourth. 
The  rami  of  the  pubes  and  ischium  unite  about  the  8th  year.  The 
acetabulum  is  all  bony  about  the  17th  year.  All  the  epiphyses  unite  to 
the  main  bone  about  the  25th  year. 

THE  PELVIS  IN  GENEBAL. 
Nomenclature.  —  The  pelvis  is  named  from  its  resemblance  to  a  basin 


The  French  call  it  '  le  bassin';  and  in  old  English  works  it  is 
often  spoken  of  as  '  the  basin/  When  accoucheurs  speak  of  the  true  pelvis, 
they  mean  all  below  the  brim.  All  above  the  brim 
they  call  the  false  pelvis.  By  the  brim  is  under- 
stood the  'linea  ilio-pectinea/  Again,  they  speak 
of  the  upper  opening  or  '  inlet/  and  the  lower 
opening  or  '  outlet  '  of  the  pelvis. 

Pelvis  a  Lever  of  the  First  Order.—  The 
pelvis  forms  a  great  arch  of  bone  which  supports 
the  trunk,  and  transmits  the  weight  of  it  to  the 
lower  limbs.  It  contains  and  protects  the  pelvic 
viscera,  and  some  of  the  abdominal.  It  acts  as  a 
lever  of  the  first  order  in  balancing  the  trunk  on 
the  head  of  the  thigh-bone,  as  when  we  stand  upon 
one  leg.  But  the  most  obvious  action  of  the  pelvis 
as  a  lever  of  the  first  order,  is  when  we  raise  the 
body  from  the  stooping  to  the  erect  attitude.  In 
FIG.  29.-The  Pelvis  a  Lever  this  action  the  fulcrum  F,  as  seen  in  Fig.  29,  is 

of  the  First  Order.  ,,        ,  .      .    .  .,  .    .  ,    „,    .      .,  ,         . 

at  the  hip-joint;  the  weight  W  is  the  trunk  of 

the  body;  and  the  power  is  fixed  to  the  tuberosity  of  the  ischium,  P. 
The  power  in  this  case  is  the  contraction  of   the  hamstring  muscles. 


PLATE  XXX II. 


Sacro-iltaa  articulation 


Section  th.ro  u^in  the  -up-perpart  cPthe  Sacrum  anc3  Ilia.. 

atian  of  the 


PELVIC    x 


THE   PELVIS    IN    GENERAL.  147 

This  is  a  very  good  example  of  a  muscle  answering  a  double  purpose. 
The  hamstring  muscle,  represented  in  the  figure,  is  the  biceps.  When 
its  fixed  point  is  below,  i.e.  at  the  fibula,  the  muscle  can  raise  the  body 
from  the  stooping  position.  When  its  fixed  point  is  at  the  pelvis,  it 
serves  to  bend  the  knee.  In  the  latter  case,  however,  the  muscle  acts 
upon  a  lever  of  the  third  order. 

Under  the  head  of  pelvis  in  general  come — 1.  Its  mechanism  as  an 
arch;  2.  Its  obliquity  with  regard  to  the  spine;  3.  Its  axis;  4.  The 
diameters  of  the  inlet  and  outlet;  5.  The  difference  between  the  male 
and  the  female  pelvis. 

Pelvic  Arch:  its  Strength. — Its  mechanism  as  an  arch  is  best 
shown  by  sawing  off  the  wings  of  the  ilia,  as  in  Plate  XXXII.  Such  a 
section  shows  the  following  points: — The  sacrum  forms  the  broad  key- 
stone of  the  arch,  and  supports  the  weight  of  the  spine.  Now  the  sa- 
crum being  set  very  obliquely,  the  weight  tends  to  thrust  it  downward  and 
backward.  This  tendency  is  resisted  by  the  sacrum  being  doubly  wedged, 
that  is,  wedged  from  above  downward,  and  from  before  backward;  thus, 
unless  the  ilia  give  way,  which  they  never  do,  the  sacrum  cannot  be  dis- 
located backward.  But  this  is  not  all:  a  reciprocal  irregularity,  or  slight 
'  dovetailing,'  between  the  articular  surfaces  of  the  sacrum  and  ilium, 
and  in  all  cases  a  '  bite '  in  front  formed  by  the  edge  of  the  ilium,  prevent 
dislocation  of  the  sacrum  forward. 

Observe,  in  the  next  place,  that  the  inclination  of  the  arch  is  such 
that  the  weight  is  transmitted  in  a  perpendicular  plane  to  the  heads  of 
the  thigh-bones.  Again,  the  thickest  and  strongest  part  6f  the  arch  is 
precisely  in  the  line  of  pressure.  Lastly,  there  are  three  '  buffers '  which 
break  shocks;  one  at  the  pubic  symphysis,  the  other  two  at  the  sacro- 
iliac  symphyses. 

Secondary  Arches. — From  the  main  arch,  two  secondary  arches 
proceed,  one  on  either  side:  these  are  the  '  sitting  arches,'  and  the  sum- 
mit of  each  is  at  the  tuberosity  of  the  ischium. 

The  following  is  a  good  instance  of  the  enormous  jreight  the  pelvic 
arch  will  bear  without  injury,  provided  the  weight  be  applied  along  tlie 
arch.  A  wagon  wheel  passed  over  a  man's  pelvis  from  side  to  side,  imme- 
diately over  the  symphysis  pubis.  The  man  stated  that  the  wagon  with 
the  load  in  it  weighed  5  tons  7  cwt.  There  was  no  injury  beyond  an  ecchy- 
mosis  of  the  scrotum  and  the  upper  part  of  the  thighs.  After  three  weeks, 
the  man  left  the  Hospital  well,  with  the  exception  of  a  slight  lameness. 


148 


HUMAN    OSTEOLOGY. 


Obliquity  of  the  Pelvis. — In  the  erect  attitude  the  line  of  gravity 
of  the  spine  falls  perpendicularly  on  the  sacrum,  as  shown  in  the  line 
a  ft,  Fig.  30.  With  this  perpendicular,  the  inclination  of  the  pelvis  forms 
an  angle  (a  ~b  c,  Fig.  31)  of  144°  in  the  male,  and  140°  in  the  female. 
Now  this  angle  is  such,  that  the  line  of  gravity  falls  through  the  acetab- 
ulum,  and  consequently  the  weight  is  transmitted  directly  on  to  the 


FIG.  30.— Line  of  Gravity  of  the  Body. 


FIG.  31.— Angle  of  Inclination  of  the  Pelvis,  144°. 


heads  of  the  thigh-bones.  For  all  practical  purposes,  one  may  ascertain 
the  proper  obliquity  of  the  pelvis  by  holding  it  so  that  the  '  notch '  shall 
be  the  lowest  part  of  the  acetabulum  (p.  139).  The  end  of  the  coccyx 
will  then  be  about  half  an  inch  higher  than  the  lower  part  of  the  sym- 
physis  pubis. 

Axes  of  the  Pelvis.-^-The  axis  of  the  brim  of  the  pelvis,  that  is,  a 
line  passing  at  right  angles  through  the  centre  of  its  plane,  if  prolonged, 
would  pass  from  «the  coccyx  to,  the  umbilicus.  The  axis  of  the  outlet 
would  fall  on  the  promontory  of  the  sacrum.  The  axis  of  the  cavity 
would  form  a  curve  nearly  corresponding  with  the  curve  of  the  sacrum. 
In  all  operations  about  the  pelvis,  it  is  of  great  importance  to  bear  in 
mind  its  different  axes.  As  a  useful  practical  rule,  we  may  say,  that  the 
axis  of  the  pelvis  corresponds  with  a  line  drawn  from  the  anus  to  the 
umbilicus. 


THE  PELVIS  IN  GENERAL.  149 

Diameters  of  the  Pelvis. — The  next  point  is  the  diameters  of  the 
pelvis;  and  it  is  interesting  because  it  concerns  parturition.  The  inlet 
or  brim  of  the  pelvis  is  somewhat  heart-shaped.  Its  diameters  vary  iiore 
or  less  in  different  cases:  in  the  recent  state,  with  all  the  soft  parts  undis- 
turbed, the  following  are  about  the  average:— 

Inches. 
Antero-posterior  or  conjugate 4 

Oblique  (from  sacro-iliac  symphysis  to  acetabulum)      .        .     4f 
Transverse 4f 

Thus  the  longest  diameter  of  the  brim  is  the  transverse.     In  this  direction 
the  long  diameter  of  the  head  of  the  child  enters  the  pelvis. 

The  shape  of  the  outlet,  in  the  recent  state,  is  like  a  lozenge,  since 
the  two  ischiatic  notches  are  blocked  up  by  the  sacro-ischiatic  ligaments. 
Its  diameters  are  as  follows: — 

Inches. 
Transverse  (from  one  tuber  ischii  to  the  other)     .        .        .4 

Antero-posterior  (from  symphysis  to  coccyx)        .         .         .     4£ 
And,  with  the  coccyx  pushed  back,  the  antero-posterior 
diameter  will  be  .        .        .        .        .  J.        .     5£ 

The  longest  diameter  of  the  outlet,  therefore,  is  from  before  backward. 

Now  the  head  of  the  child  enters  the  pelvis  in  the  transverse  diameter, 
but  descends  in  the  oblique,  till  it  presses  upon  the  spines  of  the  ischia. 
Here  its  further  progress  is  arrested  by  the  spines.  As  the  uterus  goes  on 
contracting,  the  slope  of  the  ischium  on  each  side  compels  the  head  to 
turn,  so  that  the  face  comes  to  lie  in  the  hollow  of  the  sacrum.  Conse- 
quently, the  long  axis  of  the  head  is  brought  into  the  long  axis  of  the  out- 
let, and  is  thus  easily  expelled. 

Male  and  Female  Pelvis. — The  female  pelvis  differs  very  little 
.from  that  of  the  male  till  puberty,  at  which  period  the  brim  has  a  heart- 
shaped  form  in  both  sexes.  After  puberty  the  female  pelvis  begins  to 
assume  its  sexual  characters,  which  are  the  following: — 

1.  The  sacrum  is  wider  and  less  curved; "  the  promontory  less  project- 
ing; and  the  coccyx  more  movable  than  in  the  male. 

2.  The  cavity  is  shallower,  and  all  its  horizontal  diameters  broader, 
than  in  the  male. 

19  Some  authors  state  the  reverse.  But  Albinus  ('De  SceletoO  says  truly:  'Sa- 
crum feminis  latius,  per  longitudinem  rectius,  infra  non  seque  incurvatum  in  priora.' 


150  HUMAN    OSTEOLOGY. 

3.  The  spines  of  the  ilia,  the  acetabula,  and  the  tuberosities  of  the 
ischia,  are  wider  apart  than  in  the  male. 

4.  The  symphysis  pubis  is  not  so  deep:  the  pubic  arch  has  a  much 
wider  span80  and  its  branches  are  more  shelving  than  in  the  male,  facili- 
tating parturition.     To  use  an  architectural  expression,  the  pubic  arch 
in  the  female  resembles  a  '  Norman '  arch;  in  the  male,  an  '  early  English '; 
the  sub-pubic  angle  being  about  61°  in  males  and  80°  in  females. 

Comparative  Osteology. — The  ilium  attains  its  greatest  size  in  the 
elephant  and  mastodon.  Observe  the  very  narrow  opening  in  the  pelvis 
of  the  kangaroo  (Marsupialia,  Macropus  major,  Nos.  1724,  1725).  This 
extreme  narrowness  necessitates  the  birth  of  the  young  when  they  are 
only  about  an  inch  and  a  quarter  long.  They  are  then  almost  shapeless, 
and  are  next  placed  in  a  pouch  on  the  abdomen  of  the  mother,  with  the 
nipple  firmly  fixed  in  their  mouths  until  they  are  as  far  developed  as 
the  young  of  other  animals  at  birth.  It  will  thus  be  seen  that  the 
mammae  of  the  kangaroo  open  into  the  pouch.  The  young  are  attached 
to  a  long  nipple,  and  milk  is  at  first  forced  into  their  mouths  by  the  con- 
traction of  a  muscle  spread  over  the  mammary  gland.  On  the  pubes  are 
seen  two  small  bones  which  do  not  exist  in  man.  They  are  called  the 
'  marsupial  bones/  and  are  ossifications  or  chondrifications  of  the  internal 
pillars  of  the  external  abdominal  rings. 

In  the  extinct  Mastodon  and  Megatherium  the  great  sciatic  notch  is 
converted  into  a  foramen  apparently  by  the  ossification  of  the  sacro-sciatic 
ligament. 

In  the  Hippopotamus  the  transverse  ligament  of  the  acetabulum  is 
completely  ossified,  and  the  notch  becomes  a  bony  tunnel. 

In  cetacea  the  pelvis  is  only  represented  by  a  small  flat  bone  on  each 
side  of  the  anus,  suspended  in  the  soft  parts;  and  there  is  never  more 
than  a  trace  of  hind-limb  bones.  The  manatee  (No.  2647  A)  has  no  pelvis. 

In  birds  the  acetabulum  is  perforated,  the  ischiatic  notch  is  converted 
into  a  complete  foramen,  and  there  is  no  symphysis  pubis,  excepting  in 
the  ostrich. 

The  bones  forming  the  os  innominatum  remain  distinct  throughout 
life  in  some  of  the  lower  animals.  In  No.  1011  (Testudo  elephantapos) 
these  bones  will  be  seen  to  be  fairly  distinct.  They  articulate,  but  do  not 
coalesce  perfectly  as  in  man. 

80  In  his  lectures  '  On  the  Comparative  Anatomy  of  Man,'  1877,  Professor  Flower 
gives  61°  as  the  mean  subpubic  angle  in  men,  80°  in  women. 


n  \VF  \\xii.. 


THE    FEMUR.  151 

In  Ruminants,  Pachydermata,  and  Solidungula,  the  pelvis  is  large  and 
gives  attachment  to  huge  glutei  muscles.  This  accords  with  the  extensive 
development  of  the  great  trochanter  of  the  femur,  to  which  these  muscles 
are  attached. 

Although  in  snakes  generally,  there  is  no  sternum,  upper  limb,  or 
sacrum,  nor  any  appearance  of  hind  legs,  yet,  in  a  few  instances,  viz. 
typhlops,  python  regiua,  and  tortrix,  there  are  rudiments  of  hind  limbs 
in  the  skeleton. 


THE   FEMUR. 

(PlATKS  XXXIII.,  XXXIV.) 

Length  and  Direction. — The  thigh-bone  is  the  longest  ana  strong- 
est of  all  the  bones.  Its  great  length,  in  comparison  with  the  other  bones 
of  the  leg,  is  characteristic  of  the  human  skeleton.  In  consequence  of 
this  comparative  length,  and  of  the  shortness  of  the  arms,  the  ends  of  the 
fingers  in  the  white  man  do  not  reach  lower  than  the  middle  of  the  thigh- 
bone. In  the  chimpanzee  the  fingers  reach  down  to  the  knee;  in  the 
ourang,  down  to  the  ankle. 

The  direction  of  the  thigh-bone  is  not  quite  perpendicular,  but  slants, 
so  that  the  knees  are  nearer  together  than  the  hips;  by  this  means  the 
knee-joint  is  brought  nearer  the  line  of  gravity  of  the  body.  This  obli- 
quity is  necessarily  greater  in  women,  on  account  of  the  greater  breadth 
of  the  pelvis,  and  accounts  for  their  peculiar  gait. 

We  have  to  examine  the  head,  the  neck,  the  trochanters  for  the 
attachment  of  muscles,  the  shaft,  and  the  condyles. 

Head. — The  head  forms  rather  more  than  half  a  sphere,  smooth  and 
convex  on  every  part,  except  at  a  point  a  little  behind  and  Mow  its 
centre,  where  there  is  a  depression  for  the  attachment  of  the  •'  ligamen- 
tum  teres.'  It  forms  a  perfect  ball-and-socket  joint  with  the  acetabulum. 
When  crusted  with  cartilage  the  ball  fits  so  accurately  into  its  socket,  that 
it  is  retained  in  it  by  atmospheric  pressure  alone.  It  has  been  ascer- 
tained by  experiment  that  this  pressure  is  about  26  pounds;  that  is,  more 
than  equal  to  sustain  the  weight  of  the  entire  limb  with  all  its  soft  parts. 
More  than  this,  in  walking,  the  legs  swing  like  pendulums,  so  that  we 
require  very  little  muscular  force  to  advance  one  leg  before  the  other." 
?1  The  brothers  Weber,  'Mechanik  der  mensch.  Gehwerk.,'  Gott.  1836. 


152 


HUMAN    OSTEOLOGY. 


The  limb  hangs  freely  in  its  socket,  and  the  muscles  do  not  expend  any 
of  their  power  in  keeping  it  there.  Boerhaave  might  well  say,  '  in  mira- 
bili  articulatione  femoris  Creatorem  adoramus/ 

Neck :  its  Direction. — The  general  direction  of  the  '  neck '  is  up- 
ward, inward,  and  a  little  forward  from  the  shaft.  As  a  result  of  this 
direction  of  the  neck  of  the  thigh-bone,  the  lower  extremity  naturally 
turns  a  little  outward.  Everything  in  the  bones  of  the  lower  limb*  and 
the  insertion  of  its  muscles,  conforms  to  this  object.  It  is  this  which 
gives  elasticity,  freedom,  and  grace  to  the  motion  of  the  body:  we  owe 
this  to  nature,  and  not,  as  some  suppose,  to  the  dancing-master. 

In  the  adult  the  neck  is  set  on  to  the  shaft  at  a  very  open  angle,  about 
125°.  But  the  angle  varies  at  different  ages,  in  harmony  with  the 
requirements  of  the  age.  In  children  the  neck  of  the  thigh-bone  is  so 
oblique  that  it  forms  almost  a  gentle  curve  from 
the  axis  of  the  shaft,  as  seen  in  Fig.  32.  There- 
fore the  trochanters  do  not  project  nearly  so 
much  as  in  the  adult,  Fig.  33.  This  is  one  rea- 
son why  it  is  sometimes  difficult  to  determine 
the  precise  nature  of  accidents  about  the  hip  in 
children.  As  age  advances,  the  neck,  in  some 
instances,  drops  to  nearly  a  right  angle  with  the 
shaft,  as  shown  in  Fig.  34:  besides  which  its 
compact  walls  become  thinner,  and  its  cancel- 
lous  tissue  becomes  expanded.  No  wonder,  then, 
the  neck  of  the  femur  is  so  liable  to  break  in 
old  persons.  Observe  how  much  broader  the 
neck  is  in  its  vertical  diameter,  and  how  much 
thicker  the  lower  wall  is  than  the  upper,  in  order 
to  resist  vertical  pressure.  (Plate  I.)  The  part 
where  the  neck  springs  from  the  shaft  is  called 
the  '  base '  of  the  neck.  In  falls  on  the  tro- 
chanter  the  neck  is  sometimes  broken  at  the 
base,  and  driven  into  the  shaft  between  the  tro- 
chanters, forming  what  is  called  an  '  impacted '  fracture  of  the  neck. 
The  symptoms  of  such  a  fracture  are,  more  or  less  shortening  of  the 
limb,  diminished  projection  of  the  trochanter  major,  and  no  crepitus. 

Neck,  Oblique. — Since  the  great  length  and  obliquity  of  the  neck 
of  the  femur  are  peculiar  to  man,  let  us  consider  what  advantage  his 


Comparative  Obliquity  of  the 
Neck  of  the  Thigh-Bone  in  the 
Child,  the  Adult,  and  the  Aged. 
(From  Museum  of  St.  Bartholo- 
mew's Hospital.) 


PLATE  XXXI  V. 


Pbburafcor  mternus  fc.  Gemellf, 


SuvFaee  over  whicK 
flays  the  tendon  of  the 
Gluteus  rnaxi-rwus... 


Planbaris 


i •  Attachment  of  external  lateral 


External  condyl  e . 


THE   FEMUR.  153 

skeleton  gains  by  it. — 1.  It  widens  the  base  of  support  for  the  trunk ;  2. 
It  disengages  the  shaft  from  the  hip-joint,  and  thus  increases  the  range 
of  motion.  What  animal  can  separate  its  legs  so  widely  as  man?  3. 
Greater  space  is  made  for  the  adductor  muscles,  which  balance  the  pelvis 
on  the  inside  of  the  thigh;  4.  The  great  trochanter  being  removed  to  a 
distance  from  the  hip- joint,  gives  greater  leverage  to  the  powerful  gluteal 
muscles  which  balance  the  pelvis  on  the  outside;  5.  The  weight  of  the 
trunk,  instead  of  falling  vertically  on  the  shaft  of  the  femur,  is  trans- 
mitted to  it  by  an  arch. 

Trochanters,  Major  and  Minor. — The  trochanters  '  major '  and 
*  minor '  are  outstanding  processes  which  give  great  leverage  to  the  muscles 
rotating  the  thigh  (rpoxtxoo,  verto).  Observe,  they  project  behind  the 
axis  of  rotation  (which  is  the  centre  of  the  head  of  the  bone),  an  arrange- 
ment which  further  conduces  to  the  outward  rotation  of  the  lower  limb 
as  the  natural  position.  The  relation  of  the  trochanter  major  to  the 
other  bony  prominences  of  the  pelvis  deserves  especial  attention,  because 
it  is  a  great  landmark  in  determining  the  nature  of  injuries  about  the 
hip.  The  top  of  the  great  trochanter  in  the  adult  is  about  three-quarters 
of  an  inch  lower  than  the  top  of  the  head  of  the  bone,  and  nearly  on  a 
level  with  the  spine  of  the  pubes.89 

Examine  first  the  muscles  inserted  into  the  trochantep  major.  Sup- 
pose the  trochanter  to  be  square,  which  it  is  nearly  if  seen  sideways. 
(Plate  XXXIV.)  Into  the  front  part  is  inserted  the  *  gluteus  minimus,' 
into  the  upper  part  is  inserted  the  *  pyriformis ';  also  in  front  of  the  pyri- 
formis,  and  extending  backward  beneath  it,  is  the  insertion  of  the  com- 
mon tendon  of  the  '  obturator  internus '  and  '  gemelli '  (just  above  and 
anterior  to  the  digital  fossa,  Plate  XXXIV.  Fig.  1);  into  the  back  part, 
upon  an  eminence  on  the  '  posterior  inter-trochanteric  ridge '  called  the 
'linea  quadrat!,'  is  inserted  the  'quadratus  femoris';  the  lower  part  (base 
of  the  trochanter)  gives  origin  to  the  strong  tendon  of  the  '  vastus  ex- 
ternuB.*  Draw  a  diagonal  from  behind  forward  across  the  square  (there 
is  a  faint  trace  of  it  in  nature),  and  you  find  that  the  upper  triangle  gives 
insertion  to  the  'gluteus  medius/  while  the  lower  triangle  remains 
smooth  for  the  play  of  the  tendon  of  the  '  gluteus  maximus/  a  large 
'  bursa '  being  interposed.  A  smaller  bursa  occupies  the  front  of  the 
upper  triangle,  in  connection  with  the  tendon  of  the  *  gluteus  medius.' 
(Plate  XXXIV.  Fig.  2.) 

8i  See  'Medical  and  Surgical  Landmarks,'  by  the  Author,  3rd  edition,  1881. 


154  HUMAN   OSTEOLOGY. 

Digital  Fossa. — Behind  the  neck  of  the  femur,  and  beneath  the 
projecting  angle  of  the  trochanter  major,  is  a  deep  excavation,  called  the 
'  digital  fossa.'  (Plate  XXXIII.)  The  '  obturator  externus '  is  inserted 
here;  and  this  insertion  is  at  the  bottom  of  the  fossa. 

Trochanter  Minor. — The  trochanter  minor  projects  from  the  inner 
and  back  part  of  the  shaft,  just  below  the  base  of  the  neck.  Its  posterior 
part  gives  insertion  to  the  tendon  of  the  '  psoas  magnus ';  the  fibres  of  the 
'  iliacus '  mostly  join  this  tendon,  but  a  few  are  inserted  into  the  lower 
border  of  the  lesser  trochanter  toward  the  linea  aspera.  Observe  that  the 
trochanter  minor  is  directed  backward  and  that  the  muscles  inserted  into 
it  turn  the  thigh  outward  at  the  same  time  that  they  raise  it.  These  are 
the  muscles  which,  in  fracture  of  the  upper  third  of  the  shaft,  it  is  often 
difficult  to  prevent  from  tilting  up  the  upper  fragment. 

Inter-trochanteric  Ridges. — Two  oblique  ridges  extend  from  one 
trochanter  to  the  other,  the  one  in  front  of,  the  other  behind  the  base  of 
the  neck  of  the  femur.  The  anterior  '  inter-trochanteric  ridge '  gives 
attachment  to  the  powerful  ligament  (ilio-femoral)  which  covers  the  front 
of  the  capsule  of  the  hip-joint,  limits  the  extension  of  the  thigh,  and  is 
of  great  utility  in  the  erect  position,  since  it  prevents  the  pelvis  and 
trunk  from  falling  backward.  The  posterior  *  inter-trochanteric  ridge ' 
mainly  supports  the  great  trochanter.  There  is  an  eminence  on  its 
margin,  extending  downward,  behind  the  great  trochanter  called  the  '  linea 
quadrati/  the  insertion  of  the  '  quadratus  femoris '  already  alluded  to. 

Shaft  and  Linea  Aspera. — The  shaft  of  the  femur  is  slightly 
arched  with  the  convexity  forward,  by  which  a  double  advantage  is 
gained:  first,  it  is  rendered  more  springy  than  if  it  were  straight;  sec- 
ondly, more  room  is  gained  for  the  flexor  musdes  behind,  and  more 
power  for  the  extensors  in  front  of  the  shaft.  The  shaft  is  smooth  and 
cylindrical  all  round,  except  behind,  where  there  is  a  rough  longitudinal 
ridge  termed  the  '  linea  aspera.'  This  ridge  serves  as  a  buttress  to  the 
shaft,  as  well  as  for  an  attachment  of  muscles.  The  linea  aspera  is  most 
prominent  about  the  middle  third  of  the  shaft;  here  it  appears  at  first 
sight  a  single  ridge;  but  look  carefully  and  you  will  find  traces  of  two 
borders,  termed  its  external  and  internal  'lips/  About  the  lower  third 
of  the  shaft  these  lips  diverge  from  each  other,  and  may  be  traced  to  the 
*  tuberosities  *  of  the  condyles.  The  triangular  interval  between  their 
bifurcation  is  called  the  popliteal  surface  of  the  femur,  and  upon  it  the 
popliteal  artery  rests  in  its  passage  through  the  ham.  Turning  to  the 


THE   FEMTJR.  155 

upper  end  of  the  linea  aspera,83  notice  that  here  also  its  two  lips  branch 
off:  one  runs  to  the  root  of  the  lesser  trochanter,  the  other  to  the  root  of 
the  greater. 

What  has  been  said  of  the  linea  aspera,  and  the  upper  and  lower  di- 
vergence of  its  two  lips,  will  help  us  toward  understanding  the  muscles 
attached  to  it.  Take  the  outer  lip  first.  The  '  vastus  externus  '  arises  from 
it  three-quarters  of  the  way  down.  Along  the  upper  third  is  a  very 
rough  surface  for  the  insertion  of  the  gluteus  maximus.  This  part  may 
very  properly  be  called  the  '  gluteal  ridge/  Lastly,  there  is  the  origin  of 
the  short  head  of  the  biceps,  beginning  just  below  the  insertion  of  the 
gluteus  maximus,  and  extending  nearly  down  to  the  external  condyle. 

The  inner  lip  of  the  linea  aspera  gives  origin  nearly  all  the  way  down 
to  the  'vastus  internus.'  Into  its  upper  part  is  inserted  the  'pectineus/ 
then  comes  the  insertion  of  the  '  adductor  longus/  and  behind  both  is 
that  of  the  '  adductor  brevis.'  Lastly,  the  insertion  of  the  '  adductor  mag- 
nus  '  extends  all  along  the  line  from  the  base  of  the  trochanter  major  to 
the  tuberosity  of  the  inner  condyle,  including  the  adductor  tubercle, 
which  is  a  sharp  projection  of  bone,  giving  a  firm  hold  to  the  tendon. 
The  little  interval  purposely  left  in  the  drawing  (Plate  XXXIII.)  is  in- 
tended to  mark  where  the  tendon  gives  passage  to  the  popliteal  artery. 

Canals  for  Medullary  Arteries.  —  Along  the  course  of  the  linea 
aspera  are  the  orifices  of  the  two  canals  which  convey  nutrient  blood- 
vessels to  the  marrow. 

The  front  and  outer  surfaces  of  the  shaft  give  origin  to  the  '  crureus  ' 
and  to  the  little  muscular  slips  below,  which  constitute  the  '  sub-crureus/ 
The  inner  surface  gives  origin  to  part  of  the  '  vastus  internus  *  (the  other 
and  stronger  part  arising  from  the  linea  aspera).  The  origin  of  these 
muscles  does  not  occupy  the  whole  of  the  shaft.  Along  the  lower  part, 
but  more  especially  on  the  inner  side,  no  muscular  fibres  arise:  here  the 
bone  is  simply  covered  by  the  fibres  of  the  '  vasti  '  on  each  side.  This 
accounts  for  the  great  extent  to  which  an  inflamed  knee-joint  may  swell 
beneath  the  vasti,  there  being  no  resistance  to  the  distension  of  the  syno- 
vial  membrane  in  this  direction. 

Condyles  and  Inter-condyloid  Notch.  —  The  lower  part  of  the  fe- 
mur gradually  expands  to  form  the  condyles  for  the  knee-joint  (x 


83  These  '  lineae  asperse'  are  nothing  more  than  partial  ossifications  of  the  tendons 
inserted  there.  A  very  rough  '  liuea  aspera  '  is  a  character  of  age.  It  puts  one  in 
mind  of  the  '  bone  tendons'  which  one  sees  in  the  regular  anatomy  of  birds. 


156  HUMAN   OSTEOLOGY. 

a  knuckle).  The  inner  condyle  projects  much  more,  and  is  full  half  an 
inch  lower  than  the  outer,  when  the  bone  is  perpendicular;  but  when  the 
bone  slants,  as  it  naturally  does,  both  condyles  are  on  the  same  level. 
This  must  needs  be,  as  the  plane  of  the  knee-joint  is  horizontal  in  adap- 
tation to  the  erect  posture.  The  condyles  are  separated  behind  by  a  deep 
notch,  the  '  inter-condyloid/  for  the  lodgment  of  the  two  '  crucial '  liga- 
ments, which  prevent  the  knee  from  being  extended  beyond  the  straight 
line:  for  the  requirements  of  this  joint  do  not  admit  of  any  bony  promi- 
nence to  limit  extension,  such  as  we  find  in  the  elbow.  These  ligaments 
(shown  in  Fig.  35)  are  attached  to  the  rough  surfaces  of  the  condyles 
facing  each  other;  the  anterior  crucial  to  the  external  condyle,  the  pos- 
terior crucial  to  the  internal.  The  marks  left  by  these  ligaments  can  be 
clearly  made  out  on  the  bone.  Notice  especially  that  the  mark  on  the 
external  condyle  is  placed  posteriorly,  that  on  the  internal,  anteriorly. 


FIG.  85.-Crucial  Ligaments  of  the  Knee. 

Trochlea  for  Patella. — The  articular  surfaces  of  the  condyles  unite 
in  front  to  form  the  pulley  (femoral  trochlea)  over  which  the  '  patella ' 
plays.  The  larger  share  of  the  pulley  is  formed  by  the  external  condyle, 
and  it  mounts  not  only  higher,  but  projects  more  than  the  inner,  pre- 
venting the  tendency  of  the  patella  to  be  dislocated  outward.  In  an 
antero-posterior  section,  each  articular  surface  would  present  something 
like  the  long  half  of  an  ellipse  (as  seen  in  Fig.  36).  The  two  woodcuts 
(35  and  36)  show  very  well  the  attachments  and  the  direction  of  the 
crucial  ligaments,  a  b,  a  c.  Being  attached  to  the  condyles  behind  the 
centre,  they  necessarily  limit  extension  beyond  the  straight  line.  But 
they  do  more;  by  crossing  like  braces  they  prevent  lateral  displacement 
of  the  tibia.  In  the  erect  attitude,  the  flatter  part  of  the  ellipse  rests  on 
the  shallow  excavation  of  the  tibia,  and  all  the  ligaments  are  on  the 
stretch;  but  when  the  knee  is  «bent,  the  more  convex  part  of  the  ellipse 
rests  on  the  tibia,  and  admits  of  a  certain  amount  of  rotation,  all  the 
ligaments  being  loose. 


THE   FEMUR.  157 

Tuberosities. — To  the  '  tuberosities '  (external  and  internal)  of  the 
condyles  are  attached  the  lateral  ligaments  of  the  joint.  These  tuberosi- 
ties are  situated  nearer  to  the  back  than  to  the  front  part  of  the  condyle. 
The  result  of  this  is,  that  the  ligaments  are  fixed  behind  the  centre  of 
motion,  so  that  they  become  stretched  when  the  joint  is  extended.  This 
arrangement  increases  the  strength  of  the  knee. 

There  is  an  impression  behind  the  internal  condyle  denoting  the  ori- 
gin of  the  inner  head  of  the  '  gastrocnemius ';  and  another,  behind  the 
external  condyle,  where  the  outer  head  of  this  muscle  and  the  '  plantaris ' 
arise.  On  the  outer  surface  of  the  external  condyle,  immediately  below 
the  outer  tuberosity,  is  a  depression  for  the  origin  of  the  'popliteus.' 
(Plate  XXXIV.  Fig.  3.) 

Ossification. — The  femur  is  ossified  from  three  primary  centres  (one 
for  the  shaft  and  neck,  and  one  for  each  articular  end),  and  two  sec- 
ondary centres,  one  for  each  trochanter.  (See  Plate  IV.)  The  centre  for 
the  shaft  appears  about  the  seventh  week  of  foetal  life.  The  centre  of 
the  lower  epiphysis  does  not  appear  until  within  the  last  fifteen  days 
of  the  full  term  of  gestation.  Hence  the  existence  of  this  centre  enables 
us  to  pronounce  with  something  like  certainty  as  to  the  age  of  a  foetus. 8* 
It  is  the  only  epiphysis  in  which  ossification  commences  before  birth. 
As  this  is  the  first  of  all  the  epiphyses  to  ossify,  so,  in  accordance  with 
the  general  law,  it  remains  the  longest  a  separate  piece.  The  epiphysis 
at  the  upper  end  of  the  femur  includes  only  the  head  of  the  bone,  and 
begins  to  ossify  about  one  year  after  birth.  The  great  trochanter  begins 
to  ossify  about  the  third  or  fourth  year;  the  lesser  about  the  fourteenth. 
All  the  pieces  have  united  about  the  age  of  twenty-one. 

Right  or  Left  ? — This  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body  if  he  hold  the  rounded  head  up- 
ward, and  turn  it  inward  for  articulation  with  the  acetabulum;  while  the 
linea  aspera  is  behind. 

Comparative  Osteology. — In  the  horse,  the  rhinoceros,  and  the 
tapir  (Perissodactyla)  the  gluteal  ridge  is  so  largely  developed  that  it  has 
received  the  name  of  a  '  third  trochanter.'  The  lower  end  of  the  femur 
in  most  mammals  presents  three  separate  articular  surfaces,  viz.  the 
patellar  articulation  and  two  condyles.  In  man  these  three  are  blended 
into  one,  although  there  can  be  seen  a  trace  of  the  separation  along  the 

84  Concerning  the  bearing  of  Osteogeny  on  forensic  medicine,  see  '  Medecine 
legale,'  by  M.  Orflla. 


158  HUMAN    OSTEOLOGY. 

lower  border  of  the  surface  for  the  patella.  The  actual  separation  in  man 
does  exist  in  the  foetus,  but  becomes  obliterated,  the  three  articulations 
merging  into  one.  The  ligamenta  alaria  and  the  ligamentum  mucosum 
are  the  only  remains  of  the  originally  separate  synovial  membranes  of  the 
knee-joint. 

In  Elephants  (Proboscidia)  when  standing,  the  bones  of  the  leg  and 
thigh  are  vertical,  as  in  man. 

If  you  examine  the  femurs  of  birds  you  will  find  they  have  but  one 
trochanter,  viz.  that  corresponding  to  our  trochanter  major. 

In  two  or  three  serpents,  e.g.  Python  Tigris  (No.  602),  Python  Eegius 
(No.  629),  there  are  rudimentary  hind  limbs  ending  in  hook-like  claws 
sheathed  in  horn.  These  claws  are  put  in  action  by  certain  muscles, 
and,  serving  as  antagonists  to  the  tail,  give  it  greater  prehensile  power. 

The  ventral  fins  of  fish  correspond  to  the  hind  limbs  of  other  animals. 


THE  PATELLA. 
(PLATE  XXXV.) 

Shape  and  Use. — The  patella  is  the  largest  and  best  example  of  a 
'  sesamoid '  bone.  It  is  developed  in  the  extensor  tendon  of  the  knee, 
where  it  protects  the  knee-joint,  and  increases  the  power  of  the  ex- 
tensor muscles  by  enabling  them  to  act  at  a  greater  angle.  It  is  a  princi- 
ple in  mechanics  that  the  efficiency  of  a  force  which  acts  upon  a  lever  is 
greatest  when  its  direction  is  at  right  angles  to  the  lever,  and  that  the 
force  decreases  as  the  obliquity  of  its  direction  is  increased.  In  shape,  the 
patella  is  triangular,  with  rounded  angles,  the  apex  pointing  downward. 

Its  Two  Surfaces. — Its  anterior  surface  is  convex,  and  marked  by 
longitudinal  streaks,  indicative  of  the  insertion  of  the  fibres  of  the  exten- 
sor tendon. 

Its  posterior  surface  is  smooth,  and  crusted  in  the  recent  state  with  car- 
tilage, in  order  to  play  upon  the  trochlea  of  the  femur.  It  is  divided  by  a 
vertical  ridge  adapted  to  the  groove  in  the  femur,  and  on  each  side  of  the 
ridge  are  the  articular  '  facets '  corresponding  to  the  condyles  of  the  femur. 

Ossification. — The  patella  is  developed  from  a  single  centre,  which 
appears  about  the  second  year.  It  is  not  fully  ossified  until  the  age  of 
fourteen  or  fifteen. 

The  patella,  thus  serving  a  mechanical  purpose  in  the  substance  of  the 
extensor  tendon,  is  liable  to  be  broken  by  a  sudden  and  violent  action  of 


PLATE  XXXV. 


TIBIA 


Groove  for  -tenclons  of 
Tibialis  posticus  and 
Flexor  lonbus  <3ipitorm 


Posterior  view. 


PLATE  XXXV. 


TIBIA. 


FIBULA 


Inner  facctte 


Pitdla. 


Internal  malleolu*. 


Anterior  view. 


THE    TIBIA.  159 

the  extensor  muscles,  as  in  making  a  strong  effort  to  regain  the  balance 
of  the  body  in  danger  of  falling  backward.  In  this  position — that  is, 
when  the  knee  is  half-bent — the  upper  part  of  the  patella  is  not  sup- 
ported by  its  trochlea:  there  is  a  hollow  under  it,  and  here  the  patella 
snaps  transversely,  like  a  stick  broken  across  the  knee.  The  broken 
ends  separate  widely,  and  therefore  in  these  transverse  fractures  reunion 
takes  place  by  ligamentous  substance,  not  by  bone. 

But  even  when  the  knee  is  extended,  violent  muscular  contraction  is 
able  to  snap  the  patella.  Desault  speaks  of  both  patellae  being  broken  by 
convulsions  in  a  patient  after  he  had  been  cut  for  the  stone.  Opera  dancers 
sometimes  break  the  patella  in  practising  the  step  called  the  'entrechat.' 

Right  or  Left  ? — One  has  but  to  feel  one's  own  knee  to  find  that  the 
patella  articulates  much  more  extensively  with  the  outer  condyle  of  the 
femur  than  with  the  inner.  The  larger  facet  of  the  articular  surface  is 
therefore  external;  the  apex,  for  the  attachment  of  the  ligamentum 
patellae,  points  downward. 


THE  TIBIA. 

(PLATE  XXXV.) 

Situation  and  Direction. — The  tibia  is  the  larger  of  the  two  bones 
of  the  leg,  and  is  placed  on  the  inner  side.  It  entirely  supports  the  con- 
dyles  of  the  femur,  and  transmits  the  weight  of  the  body  to  the  foot.  Its 
direction  is  not  oblique  like  the  femur,  but  vertical;  so  that  in  well- 
formed  legs  the  two  tibiae  should  be  parallel.  Let  us  examine  in  succes- 
sion the  upper  end,  the  shaft,  and  the  lower  end. 

Head. — The  upper  end  is  called  the  '  head '  of  the  tibia.  It  is  very 
broad  in  the  transverse  direction  for  the  support  of  the  condyles  of  the 
femur:  this  great  breadth  is  another  peculiarity  of  the  human  skeleton. 
The  two  articular  surfaces  for  the  condyles  are  very  shallow  in  the  dry 
bone,  but  slightly  deepened  in  the  recent  state  by  discs  of  fibro-cartilage 
(termed  the  '  semilunar  cartilages ').  These  cartilages  convert  the  shallow 
articular  surfaces  of  the  tibia  into  variable  sockets;  that  is,  sockets 
which  adapt  themselves  to  the  varying  forms  of  the  condyles  in  flexion 
and  extension  of  the  knee.  The  outer  articular  surface  is  round;  the 
inner  is  oval,  with  the  long  diameter  from  before  backward,  in  adapta- 
tion to  the  internal  condyle.  Between  the  articular  surfaces  is  a  projection 
termed  the  '  spine,'  which  is  generally  topped  by  two  little  '  tubercles.' 


160  HUMAN    OSTEOLOGY. 

In  front  of  the  spine  is  the  depression  in  which  the  anterior  crucial  liga- 
ment is  attached,  and  behind  the  spine  is  another  much  larger,  in  which 
the  posterior  crucial  ligament  is  attached.     These  depressions  serve  al 
for  the  attachments  of  the  semilunar  cartilages. 

Tuberosities,  External  and  Internal. — The  lateral  masses  which 
support  the  articular  surfaces  are  called  the  '  tuberosities '  of  the  tibia. 
The  external  tuberosity  has  at  its  back  part  a  small  articular  surface  for 
the  head  of  the  fibula:  this  articular  surface  is  on  a  kind  of  bony  ledge, 
and  its  direction  is  oblique.  The  internal  tuberosity  is  much  larger,  and 
projects  more  than  the  external.  It  has  a  groove  behind  for  the  insertion 
of  the  '  semi-membranosus/  About  one  inch  and  a  half  below  the  head 
of  the  tibia,  and  in  front  of  it,  is  the  '  tubercle '  for  the  insertion  of  the 
common  extensor  tendon  of  the  leg  (ligamentum  patellae).  This  inser- 
tion takes  place  into  the  lower  part  of  the  tubercle,  which  is  rough;  the 
upper  part  is  smooth,  to  allow  the  easy  play  of  the  tendon  (a  bursa  being 
interposed  between  the  tendon  and  the  bone). 

Shaft.— The  shaft  of  the  tibia  is  triangular  on  section.  It  is  a  little 
twisted  outward,  determining  the  obliquity  of  the  foot;  consequently  the 
inner  malleolus  advances  a  little  more  than  the  outer.  This  disposition 
corresponds  with  the  obliquity  of  the  neck  of  the  femur,  the  position  of 
its  trochanters,  and  the  oblique  direction  of  the  muscles;  the  result  of  all 
being  to  give  a  natural  inclination  outward  to  the  lower  extremity.  The 
narrowest  part  of  the  shaft  is  about  the  lower  third.  This  is  the  part 
most  frequently  broken. 

The  internal  surface  is  subcutaneous.  Notice  on  it,  below  the  in- 
ternal tuberosity,  the  insertions  of  the  '  sartorius/  the  '  gracilis/  and  the 
'  semitendinosus.'  Behind  these  is  a  rough  surface  for  the  attachment  of 
the  internal  lateral  ligament  of  the  knee. 

The  external  surface  is  slightly  hollowed  along  its  upper  half  for  the 
origin  and  lodgment  of  the  '  tibialis  anticus ':  its  lower  part  is  turned 
forward,  presenting  a  smooth  surface  for  the  play  of  the  tendons  which 
run  over  the  front  of  the  ankle-joint. 

The  posterior  surface  presents  along  its  upper  third  a  rough  line 
('  soleal  ridge  ')  slanting  from  the  outer  toward  the  inner  side.  It  marks 
part  of  the  tibial  origin  of  the  '  soleus ';  the  remainder  of  this  origin  runs 
down  the  inner  edge  of  the  shaft  to  the  extent  of  about  three  inches. 
This  origin  is  important,  since  it  concerns  the  operation  of  tying  the 
posterior  tibial  artery.  Above  the  '  oblique  line '  is  a  triangular  surface, 


THE    TIBIA.  161 

indicating  the  insertion  of  the  '  popliteus.'  The  surface  of  the  bone 
below  the  ridge  is  occupied,  internally,  by  the  origin  of  the  '  flexor  longus 
digitorum';  externally,  by  part  of  the  origin  of  the  '  tibialis  posticus.' 
Just  below  the  line  is  the  canal  for  the  medullary  artery.  It  is  the 
largest  of  all  the  like  canals  in  the  long  bones,  runs  very  obliquely  from 
above  downward,  and  when  divided  in  amputations  sometimes  occasions 
troublesome  haemorrhage.  A  nerve  has  often  been  traced  through  this 
canal  with  the  artery  into  the  medullary  cavity. 

Edges. — With  regard  to  the  edges  of  the  tibia,  the  anterior,  called 
the  '  crest/  or  '  shin/  is  very  sharp,  and  readily  felt  beneath  the  skin,  but 
only  along  the  upper  two-thirds  of  the  shaft:  along  the  lower  third  the 
front  of  the  bone  is  flattened,  for  the  passage  of  the  extensor  tendons  and 
the  anterior  tibial  vessels  and  nerve.  The  external  edge  looks  toward 
the  fibula,  and  gives  attachment  to  the  interosseous  membrane  (repre- 
sented by  the  dotted  line  in  Fig.  37)  which  connects  the  two  bones.  The 


FIG.  37.  FIG.  38. 

FIG.  37.— Section  through  the  Tibia,  T,  and  Fibula,  F,  to  show  the  thickness  of  their  Walls. 
FIG.  38.— Section  to  show  that  the  Plane  of  the  Ankle-joint  is  Horizontal. 

internal  edge  runs  from  the  hinder  part  of  the  head  of  the  tibia  down  to 
the  inner  malleolus.  It  gives  attachment  to  the  deep  fascia  covering  the 
muscles  of  the  back  of  the  leg,  beneath  those  of  the  calf. 

If  the  direction  of  the  force  in  running,  leaping,  or  walking  be  con- 
sidered, it  will  be  seen  that  the  chief  strain  on  the  tibia  is  at  the  crest  or 
anterior  border — the  shin.  This,  therefore,  is  by  far  the  strongest  and 
densest  part  of  the  bone. 

Lower  End. — The  lower  end  of  the  tibia  is  expanded  transversely  to 
form  a  hinge- joint  with  the  astragalus.  Its  articular  surface  is  concave 
from  before  backward;  but  the  transverse  plane  of  the  joint  is  horizontal 
(as  seen  in  Fig.  38),  like  that  of  the  knee,  for  the  better  support  of  the 


162  HUMAN     OSTEOLOGY. 

weight  of  the  body.  The  joint  is  secured  on  the  inner  side  by  the  pro- 
jection termed  the  '  malleolus  internus.'  The  outer  side  of  this  projection 
is  smooth  and  crusted  with  cartilage,  and  articulates  with  the  lateral 
surface  of  the  astragalus;  the  inner  is  subcutaneous.  At  its  apex  there  is 
a  deep  notch  for  the  attachment  of  the  internal  lateral  ligament  of  the 
ankle;  and  behind  it  is  a  longitudinal  groove,  which  transmits  the  ten- 
dons of  the  '  tibialis  posticus'  and  the  '  flexor  longus  digitorum.'  Exter- 
nal to  this  groove,  there  is,  in  some  bones,  a  slight  depression  for  the 
tendon  of  the  flexor  longus  pollicis. 

Lastly,  on  the  outer  surface  of  the  lower  end  is  the  rough  excavation 
for  the  reception  of  the  fibula.  There  is  no  sensible  movement  between 
the  bones,  but  just  enough  to  give  a  slight  amount  of  elasticity.  The 
security  of  the  ankle  requires  that  they  be  firmly  riveted  together  by  a 
strong  interosseous  ligament;  and  their  contiguous  surfaces  are  found  to 
be  rough,  marking  the  attachment  of  such  a  ligament. 

The  ankle  joint  is  such  a  perfect  hinge  that  when  the  foot  is  at  right 
angles  to  the  tibia,  as  in  standing,  no  lateral  movement  whatever  is  per- 
mitted; but  when  the  foot  is  extended,  a  very  slight  lateral 
movement  can  take  place  between  the  tibia  and  the  astrag- 
alus, owing  to  the  astragalus  being  narrower  behind  than 
in  front. 

Ossification. — The  tibia  is  ossified  from  three  cen- 
tres: one  for  the  shaft,  and  one  for  each  end.     The  centre 
for  the  shaft  appears  at  the  seventh  week  of  foetal  life. 
The  one  for  the  upper  end,  which  (see  Fig.  39)  includes 
the  tubercle,  appears  just  before  or  just  after  birth,  nearly 
li    \          as  early  as  the  lower  epiphysis  of  the  femur.     The  centre 
JK     \         of  the  lower  end  appears  about  the  second  year.      The 
.Tr^^L       epiphyses  do  not  unite  with  the  shaft  till  the  age    of 

twenty  or  upward. 

-Epiphy-  Right  or  Left  ? — This  bone  will  be  in  the  same  posi- 
sesof  theWbia,  tjon  &s  ^e  correSpOnding  one  in  the  student's  body  if  he 
hold  the  crest  forward,  the  head,  or  large  end,  upward,  and  the  articu- 
lation for  the  fibula  outward. 

Comparative  Osteology. — The  tubercle  of  the  tibia  is  very  largely 
developed  in  the  rhinoceros,  but  in  the  elephant  there  is  no  trace  of  it. 
The  high  and  expanded  crest  in  the  ^)ig,  camel,  and  tapir  are  remarkable. 


THE    FIBULA.  163 

In  the  higher  quadrumana,  as  the  gorilla,  chimpanzee,  and  ourang  outan, 
the  tubercle  and  crest  are  flattened.  (For  all  these  specimens  see  the 
Separate  Series.) 


THE  FIBULA. 
(PLATE  XXXV.) 

Relations  of  Tibia  to  Fibula.— The  *  fibula*  (a  clasp)  is  the  outer 
of  the  two  bones  of  the  leg.  Though  quite  as  long  as  the  tibia,  it  is  a 
slender  bone,  and  does  not  sustain  any  of  the  weight  of  the  body.  The 
upper  end  is  placed  on  a  lower  level  than  the  knee  joint,  and  forms  no 
part  of  it;  but  the  lower  end  projects  considerably  below  the  tibia,  and 
constitutes  the  outer  ankle.  The  bone  not  only  secures  the  ankle  exter- 
nally, but  gives  additional  extent  of  origin  to  the  powerful  muscles  of 
progression.  Look  well  at  the  relative  position  of  the  two  bones  of  the  leg 
in  an  articulated  skeleton.  The  fibula  articulates  with  the  outer  and  back 
part  of  the  head  of  the  tibia,  and  the  shaft  of  the  fibula  arches  backward, 
while  that  of  the  tibia  arches  forward:  the  result  of  this  is,  that  the  fibula 
lies  very  much  in  the  background,  except  at  its  lower  part,  where  it  ad- 
vances to  form  the  malleolus  externus.  A  knowledge  of  this  relative  bear- 
ing of  the  two  bones  is  important  in  the  adjustment  of  fractures,  but  more 
especially  in  the  performance  of  flap-amputations;  and  for  this  reason: 
that  the  knife,  introduced  from  the  tibial  side,  is  apt,  unless  properly  di- 
rected, to  pass  between  the  two  bones,  instead  of  behind  them:  and  this  is 
the  more  likely,  since  the  plane  of  the  posterior 
surface  of  the  tibia  slants  considerably  in  front  of 
the  fibula.  The  relative  position  of  the  two  bones, 
as  well  as  their  relative  thickness,  is  shown  by  a 
transverse  section  (Fig.  40).  The  dotted  line 
represents  the  interosseous  membrane. 

Head.— The  upper  end  of  the  fibula  is  called  PIG-  40" 

its  '  head/  and  can  be  felt  plainly  beneath  the  skin.  On  its  inner  side  is 
the  small  oval  surface  which  articulates  with  the  tibia.  Its  outer  side 
is  very  prominent,  and  rises  behind  into  a  short  projection  termed  the 


164  HUMAN    OSTEOLOGY. 

'  styloid  process/  This  little  process  is  significant,  because  it  probably 
tallies  with  the  olecranon.  It  forms  a  little  lever  for  the  insertion  of  the 
biceps  (one  of  the  hamstring  muscles).  Besides  this,  the  outer  part  of 
the  '  head '  gives  attachment  to  the  external  lateral  ligament  of  the  knee 
joint. 

Shaft. — The  fibula  must  be  learned  when  articulated  with  the  tibia. 
Immediately  below  the  head,  the  shaft  is  rounder  and  thinner  than  else- 
where. The  lower  three-fourths  of  the  shaft  is  triangular.  Its  three  sur- 
faces are  placed  so  that  one  (internal)  looks  toward  the  tibia;  another 
looks  outward;  the  third  looks  backward. 

Ridge  for  Interosseous  Membrane. — The  inner  or  tibial  surface 
is  divided  into  two  unequal  parts  by  a  longitudinal  ridge  which  gives  at- 
tachment to  the  interosseous  membrane  separating  the  muscles  on  the 
front  from  those  on  the  back  of  the  leg.  Now  the  grooved  surface  behind 
the  ridge  in  question  gives  origin  to  part  of  the  '  tibialis  posticus ' ;  that 
in  front  of  it  gives  origin  to  the  '  extensor  communis  digitorum '  (which 
arises  also  from  the  head  of  the  fibula  and  the  tibia),  to  the  '  extensor 
proprius  pollicis/  and  to  the  'peroneus  tertius.'  Thus,  four  muscles 
arise  from  the  inner  side  of  the  shaft;  of  these,  three  are  situated  in  front 
of  the  interosseous  membrane,  and  one  behind  it. 

The  outer  surface  of  the  shaft  gives  origin  to  the  '  peroneus  longus ' 
above  and  the  '  peroneus  brevis '  below.  Toward  the  lower  end  of  the  bone 
this  surface  inclines  backward,  and  the  tendons  of  these  two  muscles  play 
along  the  groove  behind  the  external  malleolus. 

The  posterior  surface  gives  origin  to  two  muscles  only;  namely,  along 
its  upper  third  to  the  '  soleus/  and  along  its  lower  two-thirds  to  the  '  flexor 
longus  pollicis.'  Here  is  the  canal  for  the  medullary  vessels. 

The  anterior  border  of  the  shaft  is  the  sharpest,  like  that  of  the  tibia. 
Trace  it  down  the  bone,  and  you  find  that  it  bifurcates  about  three  inches 
from  the  lower  end,  and  encloses  a  triangular  surface,  which  is  subcuta- 
neous. Here  we  feel  for  fractures  of  the  lower  part  of  the  fibula. 

Lower  End.  Malleolus  Externus. — The  lower  end  of  the  fibula 
descends  below  the  tibia  and  forms  the  '  malleolus  externus '  which  secures 
the  ankle  joint  on  the  outer  side.  It  is  not  only  longer  than  the  inner 
'  malleolus '  but  projects  more,  giving  more  power  to  the  tendons  of  the 
'  peronei/  which  play  in  a  groove  behind  it.  On  its  inner  side  is  the 
smooth,  slightly  convex,  triangular  surface  which  articulates  with  the  side 
of  the  astragalus;  and  .just  above  this  is  the  rough  surface  which  fits  into 


THE    FIBULA.  165 

the  groove  of  the  tibia,  and  gives  attachment  to  the  interosseous  mem- 
brane which  rivets  the  two  bones  together.  The  malleolus  gives  attach- 
ment to  the  three  separate  bands  of  the  external  lateral  ligament  of  ^  the 
ankle;  the  middle  band  is  attached  to  the  apex;  the  anterior  to  the  front 
edge;  the  posterior  and  strongest  to  a  surface  above  and  on  the  inner  side 
of  the  apex. 

The  tibia  and  fibula  are  so  fixed  together  at  the  ankle,  that  there  is 
no  sensible  motion  between  them;  only  just  enough  to  give  a  little  elas- 
ticity. The  office  of  guarding  the  ankle  is  performed  so  well  by  the  fibula, 
that  lateral  dislocation  rarely  takes  place  unless  the  fibula  be  broken. 
Fractures  of  the  fibula  generally  occur  about  2%  inches  from  the  lower 
end,  and  most  frequently  happen  in  consequence  of  a  violent  outward 
twist  of  the  foot,  as  in  slipping  off  the  curb-stone.  The  outer  surface  of 
the  os  calcis  comes  to  press  against  the  end  of  the  fibula;  the  result  of 
which  is,  that  the  shaft  of  the  bone  gives  way  at  the  weakest  part — that 
is,  just  above  the  ankle.  The  same  accident  may  happen  from  a  violent 
twist  of  the  foot  inward;  but  in  this  case  it  is  the  astragalus  which,  by  its 
pressure  outward,  causes  the  fibula  to  break.  This  kind  of  fracture — ac- 
companied, as  it  usually  is,  with  fracture  of  the  tip  of  the  internal  mal- 
leolus— is  one  of  the  most  frequent  injuries  about  the  ankle  received  into 
a  London  hospital.  Such  an  accident  is  commonly  called  '  Pott's  fracture,' 
after  the  celebrated  surgeon  who  first  described  it. 

Ossification. — The  fibula  has  three  centres  of  ossification;  one  for 
the  shaft,  and  one  for  each  end.  The  centre  for  the  shaft  appears  about 
the  seventh  week  of  fcetal  life.  The  lower  end  begins  to  ossify  about  the 
second  year;  the  upper  about  the  third  or  fourth.  It  is  interesting  to 
note  that  the  lower  end,  the  early  solidity  of  which  is  so  necessary,  is  the 
first  to  unite  to  the  shaft,  and  is  thus  contrary  to  the  rule  laid  down  on 
page  21. 

Right  or  Left  ? — This  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body,  if  he  hold  the  subcutaneous  trian- 
gular surface  downward  and  outward,  bearing  in  mind  that  the  apex  of  the 
triangle  runs  to  the  front  ridge  of  the  bone,  and  therefore  must  be  placed 
forward. 

Comparative  Osteology. — It  is  interesting  to  notice  the  gradual 
disappearance  of  the  fibula  in  reviewing  the  vertebrata.  In  the  horse  it 
is  reduced  to  a  mere  splint  at  the  upper  part  of  the  tibia. 

In  the  Ornithorhynchus  (No.  1699)  there  will  be  seen  a  broad  flat  pro- 


166  HUMAN    OSTEOLOGY. 

cess,  projecting  high  upward  at  the  back  of  the  fibula,  which  gives  ori- 
gin to  enormous  extensor  and  flexor  muscles,  which  work  the  paddle-like 
foot  (see  Phys.  Ser.  Mus.  Koy.  Coll.  Surg.,  No.  255  C).  A  similar  pro- 
cess exists  on  the  fibula  of  the  Echidna  (No.  1704  C).  The  fibula  of  the 
Armadillo  (No.  2335)  attains  a  great  size;  and  is  anchylosed  above  and 
below  to  the  tibia  and  enters  into  the  formation  of  the  knee  joint. 


PLATE  XXXVI. 


THE  BONES  OF  THE  FOOT. 

(PLATES  XXXVI.,  XXXVII.) 

Number  of  Bones. — There  are  twenty-six  bones  in  the  foot  (exclud- 
ing the  two  sesamoid  bones  of  the  great  toe,  and  two  others  in  connection 
with  tendons) : — In  the  tarsus,  seven — namely,  the  '  astragalus/  the  '  os 
calcis/  '  the  scaphoid,'  the  three  *  cuneiform  bones/  and  the  '  cuboid ';  in 
the  metatarsus,  five;  the  remaining  fourteen  belong  to  the  toes. 

Advantage  of  many  Bones. — The  advantage  of  so  many  bones 
entering  into  the  formation  of  the  foot  is  the  same  for  the  foot  as  for  the 
hand.  With  a  larger  number  of  joints  motion  and  elasticity  are  in- 
creased, while  the  chances  of  fracture  or  dislocation  are  lessened. 

Arches  of  the  Foot. — The  bones  of  the  foot  form  two  arches:  one, 
*  longitudinal/  extends  in  the  long  axis  of  the  foot;  the  other,  transverse, 
is  most  marked  at  the  instep.  The  longitudinal  arch  is  supported, 
t  behind,  by  the  os  calcis,  and  in  front  by  the  heads  of  the  metatarsal 
bones.  Its  height  and  span  are  greatest  on  the  inner  side  of  the  foot; 
and  gradually  decrease  toward  the  outer  side.  The  marks  made  by  wet 
feet  show  how  much  more  the  outer  border  of  the  foot  comes  in  contact 
with  the  ground  than  the  inner.  The  weight  of  the  body  falls  perpen- 
dicularly on  the  astragalus,  which  is  the  key-stone  or  crown  of  the  arch. 
Concerning  the  astragalus,  two  points  must  be  borne  in  mind: — 1.  A 
part  (the  head)  of  it  is  supported  below  by  a  remarkably  strong  and 
slightly  elastic  ligament  (calcaneo-scaphoid),  which  admits  of  its  rising 
and  falling  like  a  spring;  2.  It  is  articulated  with  the  os  calcis  and  the 
scaphoid  in  such  a  way  as  to  allow  the  lateral  motions  of  the  foot  (adduc- 
tion and  abduction).  Flexion  and  extension  of  the  foot  are  performed 
at  the  ankle  joint.  Further,  all  the  bones  of  the  foot  are  more  or  less 
movable  on  each  other,  thus  breaking  shocks  and  increasing  elasticity; 
and  yet  their  mutual  connection  is  so  well  secured,  thafc  dislocation  of  any 
one  bone  is  extremely  rare. 


168  HUMAN    OSTEOLOGY. 

Tarso-Metatarsal  Articulations. — The  second  row  of  tarsal  bones 
consists  of  four:  namely,  the  three  cuneiform  and  the  cuboid.  These 
articulate  with  the  metatarsal  bones  as  follows: — The  internal  cuneiform 
with  two,  those  of  the  great  and  second  toes;  the  middle  cuneiform  with 
one,  that  of  the  second  toe;  the  external  cuneiform  with  three,  those  of 
the  middle,  the  second,  and  fourth  toes;  and  the  cuboid  with  two,  those 
of  the  fourth  and  fifth  toes.  See  how  this  exactly  corresponds  with  the 
articulations  of  the  second  row  of  carpal  bones  with  the  metacarpals. 
Starting  from  the  great  toe,  or  thumb  side,  these  bones  articulate  with  2, 
1,  3,  and  2  metatarsal  and  metacarpal  bones  respectively. 

It  is  wonderful  what  habit  and  necessity  will  make  the  foot  accom- 
plish. Those  who  coop  it  in  tight  boots,  can 
hardly  credit  that  persons  carve,  write,  and 
even  paint  with  the  toes.  '  Pes  altera  manus  ' 
is  not  so  far  from  the  truth.  A  French  artist, 
Ducornet,  born  without  arms,  used  to  paint 
with  his  toes  pictures  worthy  of  a  place  in 
the  French  Exhibition. 

The  Foot  a  Lever  of  the  Second  Or- 
der.— The  foot  is  a  lever  of  the  second  order 

for  raising  the  body.  The  weight  is  at  the  ankle  joint  W  (Fig.  41);  the 
fulcrum  F  is  at  the  toes;  and  the  power  (which  is  the  contraction  of 
the  muscles  of  the  calf)  is  at  the  heel  P.  All  the  conditions  are  those 
of  a  lever  of  the  second  order.  The  power  and  the  weight  act  in 
opposite  directions  on  the  same  side  of  the  fulcrum.86 


THE  ASTRAGALUS. 
(PLATE  XXXVI.) 

The  Key-stone  :  its  Six  Aspects. — The  astragalus  (a 
talus,  the  knuckle-bone,  with  which  the  ancients  used  to  play  at  dice),  is 
the  key-stone  of  the  arch  of  the  foot,  and  supports  the  whole  weight  of 
the  body,  which,  in  the  erect  position,  falls  perpendicularly  upon  it  from 
the  tibia.  It  is  so  much  concerned  in  the  mechanism  of  the  spring  of 

86  There  is,  howevtr,  room  for  two  opinions  on  the  question;  some  calling  the 
foot  a  lever  of  the  first  order. 


THE    ASTRAGALUS.  169 

the  foot,  that  the  Germans  call  it  the  '  spring  bone.'  To  examine  it 
thoroughly  study  its  six  aspects. 

Superior  Aspect. — Its  superior  surface,  broad  and  horizontal  in  the 
transverse  direction,  the  best  adapted  for  the  erect  posture,  presents  a 
pulley-like  convexity  in  the  antero-posterior  direction,  which  articulates 
with  the  tibia,  and  admits  of  the  flexion  and  extension  of  the  ankle.  In 
front  of  this  is  the  rough  surface  or  e  neck,'  for  the  attachment  of  liga- 
ments. This  pulley-like  surface  is  at  least  one-fifth  of  an  inch  broader 
in  front  than  behind.  This  prevents  dislocation  of  the  astragalus  back- 
ward, which  would  otherwise  be  a  more  frequent  occurrence,  considering 
the  direction  of  the  force  in  walking,  running,  or  leaping.  In  conse- 
quence of  this  greater  narrowness  of  the  astragalus  behind,  the  ankle  joint 
admits  of  a  very  slight  lateral  movement  when  the  foot  is  extended.  But 
there  can  be  no  lateral  movement  at  the  ankle  when  the  foot  is  at  right 
angles  to  the  tibia,  i.e.  when  we  stand  upon  it. 

Lateral  Aspects. — Each  lateral  aspect  presents  an  articular  surface 
adapted  to  the  corresponding  malleolus.  The  outer  is  much  the  larger, 
slightly  concave  from  above  downward,  and  triangular  with  the  apex 
below.  The  inner  is  comparatively  small,  rounded  in  front  and  pointed 
behind;  it  occupies  very  little  of  the  bone,  so  that  a  large,  rough  excava- 
tion is  left  below,  for  the  attachment  of  the  enormously  strong  internal 
lateral  ligament  upon  which  the  security  of  the  ankle  so  much  depends. 

Posterior  Aspect. — Its  posterior  aspect  is  narrow,  and  presents  a 
groove  running  obliquely  downward  and  inward  for  the  tendon  of  the 
flexor  longus  pollicis,  and  a  projection  on  the  outer  side  of  it  for  the 
attachment  of  the  posterior  division  of  the  external  lateral  ligament  of 
the  ankle. 

Anterior  Aspect. —  The  anterior  aspect  presents  a  large  convex 
*  head/  which  is  received  into  a  socket,  formed,  in  front,  by  the  scaphoid; 
below,  by  the  '  sustentaculum  tali '  (part  of  the  os  calcis) ;  also  by  a  strong 
and  slightly  elastic  ligament  which  fills  up  the  gap  left,  on  the  inner  side 
and  below,  between  these  bones  in  the  skeleton.  (Plate  XXXVIII.) 
Sometimes  the  under  surface  of  the  '  head  '  has  two  separate  '  facets '  to 
articulate  with  the  os  calcis.  These  are  distinctly  marked  in  children; 
and  they  become  united  in  adults,  owing  perhaps  to  the  pressure  to 
which  they  are  subjected  by  the  practice  of  wearing  high  heels. M  It  is 
this  ligament  (calcaneo-scaphoid)  which  mainly  supports  the  arch  of  the 

84  Camper. 


170  HUMAN    OSTEOLOGY. 

foot,  and  gives  it  its  spring.  If  this  ligament  yield  more  than  it  should 
do,  as  is  sometimes  the  case  in  weakly  persons,  or  in  opera-dancers,  from 
excessive  straining,  or  in  bakers,  from  carrying  heavy  weights,  down  goes 
the  arch — the  foot  becomes  flat,  and  the  astragalus  may  sink  low  enough  to 
touch  the  ground. 

Inferior  Aspect. — The  inferior  aspect  rests  on  the  os  calcis  by  two 
articular  surfaces,  one  behind  the  other,  and  separated  by  a  deep  groove 
directed  from  the  inner  side  obliquely  outward  and  forward.  Of  these 
surfaces,  the  posterior  is  by  far  the  larger,  and  placed  a  little  more  exter- 
nal than  the  anterior.  The  posterior  is  concave,  the  anterior  flat,  and 
both  of  them  slant  a  little  downward  and  forward.  The  consequence  of 
this  is,  that  when  the  foot  sustains  the  weight  of  the  body,  the  astrag- 
alus slides  a  little  forward  on  the  os  calcis,  and  presses  with  its  head 
firmly  against  the  scaphoid  bone  and  the  calcaneo-scaphoid  ligament 
underneath,  which,  being  somewhat  elastic,  yields  a  little,  so  that  the 
foot  becomes  longer.  But  this  is  not  all.  When  we  step  forward,  while 
the  foot  is  raised,  the  bones  (os  calcis  and  scaphoid)  roll  easily  below  the 
astragalus,  so  that  the  toes  may  be  directed  to  suit  the  inequalities  of  the 
ground:  but,  the  foot  once  planted,  the  body  rests  perpendicularly  on  it, 
the  astragalus  sinks  into  its  socket,  presses  the  os  calcis  backward  and  the 
metatarsal  bones  forward,  and  thus  we  have  a 
•Tibia  steady  base  of  support. 

•Fibula.  Tunnel  of  the  Tarsus.— The  groove  just 

alluded  to,  between  the  articular  surfaces  of  the 
astragalus,    corresponds    with    another    between 
•  Astragalus,  those  of    the    os    calcis.     When   the  bones   are 
together,  the  grooves  form  a  complete  tunnel  (ca- 
nalis  tarsi)  beneath  the  astragalus,  wide  on  the 
c  '     outside,  but  narrow   on  the  inside   of  the  foot 
(Fig.  42).     This  tunnel  is  occupied  in  the  recent 

FIG.  42.— Section  to  show  the 

Tunnel  of  the  Tarsus.  state  by  fat  and  by  the  strong  mterosseous  liga- 
ment which  connects  the  two  bones:  its  direction  is  obliquely  from  before 
backward,  and  permits  the  free  lateral  movements  of  the  foot,  which  take 
place,  not  at  the  ankle  joint  proper  (a  simple  hinge),  but  between  the 
astragalus  and  the  bones  with  which  it  articulates  beloiv.  The  astragalus 
cannot  be  displaced  from  the  os  calcis  without  rupture  of  the  interosseous 
ligament. 


PLATE  XXXVII. 


Tubercle  of  Scaphoid 

Tendon  of  Tib?post« 
scnda   offsets  to  all 

bones  'of  Toorsus 
fexceptAstrouj^  an.i 
•to  2nd  3rd  aauU1? 

Melattursol. 


Inner,  tendon  of 
extibrev.-digt"-1 


xtT  longua 
pollicis 


longus*  et  brevis  dicntorum 


PLATE  XXXVI 1* 


"Fig. 


Flexor  accessorlus  _ 


Groove 
Hexor  longus  polli 


Tubercle  of  Scaphoul 

Tendon  of  Hb?post« 
sends   offsets  to  all 
bones  'of  Tarsus 
fexceptAstrag?)  cu 
'to  2 na  3rd  suicU1-11 


Peroneus  l 


-Abductor  miiriim, 
digiu 

ExlerruU 
tubercle 


Flexor  cu:ce»8Cm(9 


-Abduclor  et 
Flexor  bvevis  pollici 


JFlexor 

longus  pollicis 


OS    C ALOIS,    OB   CALCANEUM.  171 

Connections. — The  astragalus  articulates  with  four  bones — namely, 
the  tibia,  the  fibula,  the  os  calcis,  and  the  scaphoid. 

Ossification. — It  is  ossified  from  a  single  centre,  which  appears 
about  the  seventh  month  of  foetal  life. 

Right  or  Left  ? — This  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body  if  he  hold  the  groove  for  the  inter- 
osseous  ligament  downward,  the  rounded  head  forward  and  on  the  inner 
side,  for  articulation  with  the  hollow  of  the  scaphoid. 


OS  CALCIS,  OE  CALCANEUM. 

(PLATES  XXXVI.,    XXXVII.) 

Use. — The  os  calcis,  or  '  calcaneum/  is  the  longest  and  strongest  of 
the  tarsal  bones.  It  transmits  the  weight  of  the  body  to  the  ground,  and 
forms  a  powerful  lever  for  the  muscles  of  the  calf.  The  nearly  horizontal 
direction  of  the  heel  is  peculiar  to  the  skeleton  of  man,  in  adaptation  to 
his  erect  position.  The  oblique  projection  in  the  hind  limb  of  a  horse, 
called  the  '  hock/  is  the  os  calcis. 

There  is  a  prevalent  opinion  that  the  negro  has  a  longer  heel  than  the 
white  man;  but  an  examination  of  a  series  of  calcanea  in  both  races 
proves  this  to  be  an  error.  Professor  Flower,  in  his  lectures  on  the 
*  Comparative  Anatomy  of  Man/  states  that  the  apparent  lengthening  in 
the  negro  is  due  to  the  smallness  of  his  calf  and  the  slenderness  of  the 
tendo-Achillis  immediately  above  the  heel. 

There  are  six  different  aspects  on  the  os  calcis. 

Superior  Aspect. — Its  superior  aspect  presents  the  two  surfaces 
which  support  the  astragalus.  Of  these,  the  posterior  is  convex  and 
larger  than  the  anterior,  which  is  concave,  long  and  narrow,  and  is  situated 
on  the  top  of  the  '  sustentaculum  tali '  (presently  to  be  described).  The 
plane  of  both  these  surfaces  is  horizontal  transversely,  the  better  to 
support  the  weight;  but,  like  those  of  the  astragalus,  they  slope  a  little, 
so  that  the  weight  is  transmitted  obliquely  downward  and  forward  upon 
the  arch  of  the  foot.  Observe  the  groove  between  the  articular  surfaces 
for  the  attachment  of  the  interosseous  ligament:  this  groove  makes,  with 
the  astragalus,  a  complete  tunnel  shown  in  Fig.  42. 

If  a  perpendicular  section  be  made  through  the  os  calcis,  it  shows  that 


172  HUMAN   OSTEOLOGY. 

the  compact  wall  is  thickest  at  the  articular  surfaces  for*the  astragalus; 
and  that,  from  these,  the  principal  septa  of  the  cancelli  radiate  toward 
the  back  and  under  part  of  the  bone;  that  is,  precisely  in  the  line  of 
pressure. 

Anterior  Aspect. — The  anterior  end  presents  a  concave  vertical 
surface,  which  articulates  with  the  cuboid  bone.  The  edge  of  this  sur- 
face projects  a  little,  superiorly;  and  the  projection  deserves  notice,  chiefly 
because  it  is  in  the  way  in  the  performance  of  '  Chopart's '  operation, 
which  consists  in  the  removal  of  all  the  bones  of  the  foot,  except  the  os 
calcis  and  astragalus.  In  some  instances  it  supports  a  third  articular 
facet  for  the  astragalus  (see  p.  153).  The  rough  tubercle,  on  the  dorsal 
surface  of  the  anterior  end,  gives  origin  to  the  '  extensor  brevis  digitorum/ 

Posterior  Aspect. — The  posterior  end,  or  'great  tuberosity,'  forms 
the  heel.  The  lower  rough  part  indicates  the  insertion  of  the  '  tendo- 
Achillis ';  while  the  smooth  part  above  indicates  the  position  of  the  bursa 
between  the  tendon  and  the  bone. 

External  Aspect. — The  external  surface  is  broad,  flat,  and  nearly 
subcutaneous.  Bather  in  front  of  the  middle  is  a  tubercle  (peroneal  tu- 
bercle) which  serves  to  keep  the  peroneal  tendons  in  place,  that  of  the 
'  peroneus  brevis '  being  above,  that  of  the  '  peroneus  longus '  below  the 
tubercle.  Behind  this  tubercle  is,  generally,  another,  much  smaller, 
for  the  attachment  of  the  external  lateral  ligament  of  the  ankle. 

Internal  Aspect. — The  internal  surface  presents  a  concavity  for  the 
safe  transmission  of  the  plantar  vessels  and  nerves.  At  its  upper  part 
is  the  process  termed  the  '  sustentaculum  tali,'  which  helps  to  support 
the  head  of  the  astragalus,  shelters  the  plantar  vessels  and  nerves,  and 
gives  attachment  to  the  calcaneo-scaphoid  ligament  and  to  some  fibres  of 
the  internal  lateral  ligament  of  the  ankle.  There  is  a  deep  groove  along 
the  under  surface  of  this  process  for  the  tendon  of  the  '  flexor  longus 
pollicis.' 

Inferior  Aspect. — The  inferior  or  plantar  surface  presents  at  its 
back  part  two  tubercles,  of  unequal  size,  the  internal  being  much  the 
larger.  They  are  the  only  parts  of  the  os  calcis  which  touch  the  ground. 
They  serve  for  the  origin  of  muscles,  and  for  the  attachment  of  the  strong 
plantar  fascia  which  protects  the  sole  of  the  foot.  There  is  also  another 
tubercle  forward  for  the  attachment  of  the  calcaneo-cuboid  ligament. 
Thus,  there  are  three  exceedingly  strong  ligaments  attached  to  the  os  cal- 
cis for  the  preservation  of  the  arch  of  the  foot — 1,  the  plantar  fascia 


THE   SCAPHOID   BONE.  173 

(which  acts  as  a  ligament);  2,  the  calcaneo-scaphoid  ligament  beneath 
the  head  of  the  astragalus;  and  3,  the  calcaneo-cuboid. 

The  muscles  arising  from  the  os  calcis  are: — '  Abductor  pollicis/  '  ab- 
ductor digiti  minimi/  '  flexor  brevis  digitorum/  '  flexor  accessorius '  (two 
heads),  and  '  extensor  brevis  digitorum. '  The '  tendo-Achillis '  is  the  only 
insertion;  unless  we  include  that  of  the  little  'plantaris/  on  the  inner 
side  of  the  tendo-Achillis,  and  a  few  fibres  from  the  tibialis  posticus  into 
the  '  sustentaculum  tali.' 

Connections. — The  os  calcis  articulates  with  two  bones,  the  astraga- 
lus and  cuboid. 

Ossification. — The  os  calcis  has  two  centres  of  ossification:  one  for  the 
great  mass  of  the  bone,  which  appears  about  the  seventh  month  of  foetal 
life;  and  another  for  the  great  tuberosity  which  is  an  epiphysis  and  ap- 
pears about  the  tenth  year.  The  epiphysis  unites  to  the  "bone  about  the 
sixteenth  year.  It  represents,  according  to  some  anatomists,  the  pisiform 
bone  of  the  wrist. 

Right  or  Left  ? — This  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body  if  he  hold  the  cubical  heel  back- 
ward, the  articulation  for  the  astragalus  upward,  and  the  sustentaculum 
tali  inward. 

THE  SCAPHOID  BOITE. 

Situation. — The  scaphoid  bone,  so  named  from  its  boat-like  form,  is 
situated  on  the  inner  side  of  the  tarsus.  It  presents,  posteriorly,  a  con- 
cave oval  surface  (the  narrow  end  being  placed  internally),  which  forms 
part  of  the  socket  for  the  head  of  the  astragalus.  Anteriorly,  it  has 
three  articular  facets  for  the  three  cuneiform  bones.  These  facets  are 
not  all  on  the  same  plane  or  of  the  same  shape:  the  inner  is  the  largest, 
and  articulates  with  the  inner  cuneiform:  the  middle  and  the  outer  facets 
are  triangular  with  the  apices  below,  to  fit  £he  middle  and  outer  cunei- 
form. Externally,  it  has  sometimes  a  small  facet  which  articulates  with 
the  cuboid  bone.  Internally,  it  has  a  very  prominent  tubercle,  which 
projects  and  can  be  readily  felt  on  the  inner  side  of  the  foot.  It  gives 
insertion  to  the  tendon  of  the  '  tibialis  posticus/  which  turns  the  foot  in- 
ward. This  tubercle  is  the  best  guide  to  the  joint  behind  it,  in  the  per- 
formance of  Chopart's  operation.  The  lower  part  of  the  scaphoid  is  very 
rough  for  the  attachment  of  the  calcaneo-scaphoid  ligament. 


174  HUMAN   OSTEOLOGY. 

Connections. — The  scaphoid  articulates  with  the  three  cuneiform 
bones  in  front,  the  astragalus  behind,  and  sometimes  with  the  cuboid. 

Ossification. — It  has  a  single  centre,  which  appears  about  the  fourth 
year. 

Right  or  Left  ? — This  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body  if  he  hold  the  concave  surface  for  the 
head  of  the  astragalus  backward,  the  tubercle  downward  and  on  the  inner 
side. 

THE  CUBOID  BONE. 

Situation. — The  cuboid  bone  is  situated  on  the  outer  side  of  the  tar- 
sus, and  is  wedged  in  between  the  os  calcis  and  the  fourth  and  fifth 
metatarsal  bones.  The  base  of  the  wedge  is  turned  toward  the  cuneiform 
bones,  so  that  the  pressure  in  the  arch  of  the  foot  is  properly  distributed. 
Suppose,  for  a  moment,  the  base  were  turned  the  other  way,  would  not 
the  lateral  thrust  from  the  external  cuneiform  bone  force  the  cuboid  out 
of  the  arch,  and  the  falling  of  the  arch  be  the  consequence? 

Surfaces. — Its  posterior  surface  is  slightly  concave  from  above  down- 
ward, and  convex  from  side  to  side,  to  articulate  with  a  corresponding 
surface  on  the  os  calcis.  Observe  that  the  plane  of  this  joint  is  the  same 
as  that  between  the  scaphoid  and  astragalus.  Hence  partial  amputation 
of  the  foot  (Chopart's  operation)  here  is  easy.  But  it  cannot  be  done  at 
one  stroke  of  the  knife,  because  the  inner  corner  of  the  cuboid  projects 
a  little  beneath  the  os  calcis,  which  tends  to  prevent  it  being  dislocated 
upward. 

Its  anterior  surface  has  two  smooth  facets,  the  inner  nearly  square,  the 
outer  triangular,  which  support  the  fourth  and  fifth  metatarsal  bones. 

Its  internal  surface  articulates  with  the  third  or  outer  cuneiform,  by 
a  flat  oval  surface,  and,  generally,  with  the  scaphoid. 

Its  inferior  surface  is  traversed  by  a  deep  groove  which  runs  obliquely 
inward  and  forward  and  lodges  the  tendon  of  the  '  peroneus  longus.'  The 
prominent  ridge  behind  the  groove,  and  the  rest  of  its  under  surface,  give 
attachment  to  the  calcaneo-cuboid  ligament.  Observe  near  the  posterior 
part  of  this  ridge  a  small  smooth  facet  (crusted  in  the  recent  state  with 
cartilage),  which  articulates  with  the  sesamoid  bone  in  the  tendon  that 
plays  in  the  groove. 

Connections. — The  cuboid  articulates  with  four  bones — the  os  calcis, 


THE    CUNEIFORM    BOXES.  175 

the  outer  cuneiform,  and  the  fourth  and  fifth  metatarsals— and  sometimes 
with  a  fifth,  namely  the  scaphoid. 

The  cuboid  gives  origin  to  parts  of  two  muscles  in  the  sole — the  '  ad- 
ductor pollicis/  and  the  '  flexor  brevis  pollicis.'  Eemember  that  the  ad- 
ductor pollicis  arises,  not  immediately  from  the  bone,  but  from  the  fibrous 
sheath  which  bridges  over  the  groove  for  the  peroneus  longus. 

Ossification. — The  single  nucleus  of  the  cuboid  bone  appears  at  birth. 

Right  or  Left  ? — This  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body  if  he  hold  the  groove  for  the  pero- 
neus longus  downward,  the  narrow  non-articular  edge  outward,  and  the 
large  concavo-convex  surface  for  articulation  with  the  os  calcis  backward. 

THE  CUNEIFORM  BONES. 

Position. — The  cuneiform  or  wedge  bones  are  placed  at  the  front 
part  of  the  tarsus,  and  are  named  the  '  internal,' '  middle/  and  *  external/ 
according  to  their  position.  Behind,  they  articulate  with  the  scaphoid; 
in  front,  with  the  three  inner  toes,  respectively.  The  bases  of  the  middle 
and  external  are  toward  the  dorsum  of  the  foot;  but  the  base  of  the  in- 
ternal is  turned  toward  the  sole,  in  order  to  form  one  of  the  buttresses  of 
the  transverse  arch  of  the  foot. 

Internal  Cuneiform. — The  internal  cuneiform  is  the  largest,  and 
supports  the  metatarsal  bone  of  the  great  toe.  Its  anterior  articular  sur- 
face is  convex,  and  kidney-shaped,  with  the  long  diameter  vertical.  In- 
feriorly,  the  thick  base  projects  into  the  sole  considerably  below  the  other 
cuneiform  bones,  giving  broad  insertion  to  the  tendons  of  the  two  muscles 
which  turn  the  sole  of  the  foot  inward,  namely,  the  '  tibialis  anticus '  and 
'  posticus.'  Externally,  it  is  slightly  concave,  and  articulates  along  its 
upper  and  posterior  margins  with  the  second  cuneiform  and  the  second 
metatarsal  bones:  internally,  it  is  convex,  and  has  a  little  smooth  surface 
over  which  the  tendon  of  the  *  tibialis  anticus '  plays.  Posteriorly,  it  ar- 
ticulates with  the  scaphoid  by  a  concave  surface,  wider  below  than  above. 

Thus  it  articulates  with  four  bones — namely,  the  scaphoid,  the  middle 
cuneiform,  and  the  two  inner  metatarsals. 

Right  or  Left  ? — This  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body  if  he  hold  the  sharp  edge  upward, 
the  rough  non-articular  surface  inward,  and  the  smaller  concave  articular 
surface  backward  to  articulate  with  the  scaphoid. 


176  HUMAN    OSTEOLOGY. 

Middle  Cuneiform. — The  second  or  middle  cuneiform  bone  is  not 
only  the  smallest  of  the  three,  but  does  not  project  so  much  as  the  others; 
consequently  the  second  metatarsal  bone,  which  it  supports  by  a  triangu- 
lar surface,  is  more  deeply  set  in  the  tarsus  than  the  other  metatarsals. 
This  is  a  point  to  be  remembered  in  removing  the  metatarsal  bones 
(Hey's  operation).  Posteriorly,  it  articulates  with  the  scaphoid  by  a  tri- 
angular surface  with  the  apex  below.  It  has  on  each  side  an  articular 
facet  for  the  adjoining  wedge  bones.  The  external  facet,  slightly  concave, 
runs  vertically  along  its  posterior  half  in  correspondence  with  the  exter- 
nal cuneiform.  The  internal  facet,  slightly  convex,  skirts  its  superior 
and  posterior  borders;  thus  presenting  a  horizontal  and  a  vertical  portion, 
in  exact  correspondence  with  the  marginal  surface  of  the  internal  cunei- 
form. It  is  one  of  the  peculiarities  of  these  wedge  bones  of  the  foot, 
that  intervals  are  left  between  their  sides,  for  the  attachment  of  the  in- 
terosseous  ligaments  which  fasten  the  bones  together. 

Connections. — The  middle  cuneiform  articulates  with  four  bones — 
the  scaphoid,  the  outer  and  inner  cuneiform,  and  the  second  metatarsal. 

Right  or  Left  ? — This  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body  if  he  hold  the  apex  of  this  wedge- 
shaped  bone  downward,  the  narrowest  side  of  the  base  forward,  and  the 
concave  side  (with  the  vertical  articular  surface  only)  outward. 

External  Cuneiform. — The  third  or  external  cuneiform  bone  articu- 
lates, externally,  with  the  cuboid  by  a  flat  oval  facet,  and  with  the  inner 
corner  of  the  fourth  metatarsal  bone;  internally,  with  the  middle  cunei- 
form and  the  second  metatarsal;  posteriorly,  with  the  scaphoid;  anteriorly, 
it  supports  the  third  (its  proper)  metatarsal  on  a  triangular  surface;  thus 
it  articulates  with  six  bones.  Notice,  especially,  the  extent  to  which  it 
juts  forward  between  the  second  and  fourth  metatarsal  bones,  so  that  it 
helps  to  support  three  metatarsals  just  as  the  os  magnum  of  the  wrist 
supports  three  metacarpals. 

The  flexor  brevis  pollicis  partly  arises  from  the  under  surface  of  the 
external  cuneiform;  and  some  of  the  fibres  of  the  tendon  of  the  tibialis 
posticus  are  inserted  into  it. 

Right  or  Left  ? — This  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body  if  he  hold  the  rough  non-articular 
surface  toward  the  dorsum  of  the  foot,  its  sharpened  end  backward,  fit- 
ting in  between  the  scaphoid  and  the  cuboid;  and  the  round  flat  surface 
for  articulation  with  the  cuboid  on  its  outer  side. 


THE    METATARSUS.  177 

Articulations  of  Tarsal  Bones. — Look  once  more  at  the  bones, 
and  remember  that  the  astragalus  articulates  with  four  bones;  the  oa 
calcis  with  two;  the  scaphoid  with  four  (sometimes  five);  the  internal 
cuneiform  with  four;  the  middle  cuneiform  with  four;  the  external  cune- 
iform with  six;  the  cuboid  with  four  (sometimes  five,  the  fifth  being  the 
scaphoid). 

Ossification  of  Tarsal  Bones. — Each  bone  of  the  tarsus  has  one 
centre  of  ossification,  except  the  os  calcis,  which  has  two.  The  os  calcis 
begins  to  ossify  about  the  sixth  month  of  foetal  life;  the  astragalus  about 
the  seventh  month;  the  cuboid  about  birth;  the  external  cuneiform  about 
the  first  year  after  birth;  the  middle  and  internal  cuneiform  and  scaphoid 
about  the  third  or  fourth  year. 

The  second  centre  (or  epiphysis)  of  the  os  calcis  is  at  the  back  part  of 
it.  It  appears  about  the  tenth  year,  and  joins  the  rest  of  the  bone  about 
puberty. 

THE  METATARSUS. 

General  Description. — The  five  metatarsal  bones  are  named  the 
first,  second,  third,  fourth,  and  fifth,  counting  from  the  inner  side.  The 
first  is  the  shortest  and  by  far  the  strongest,  and  supports  the  great  toe. 
The  second  is  the  longest;  and  from  this  the  third,  fourth,  and  fifth 
gradually  decrease  in  length.  All  are  slightly  arched  from  before  back- 
ward; in  addition  to  this,  the  three  outer  incline  a  little  sideways  toward 
the  great  toe.  The  spaces  between  them  are  termed  the  '  interosseous 
spaces/  and  gradually  decrease  in  size  toward  the  outer  side.  As  the 
metatarsal  bones  are  '  long '  bones,  we  speak  of  their  shafts  and  their 
articular  ends;  the  upper  end  of  each  being  termed  the  '  base/  and  the 
lower  or  rounded  end  the  '  head '  of  the  bone. 

Like  the  corresponding  bones  in  the  hand,  the  shafts  of  the  meta- 
tarsal bones  are  more  or  less  triangular  on  transverse  section,  being  flat 
on  the  dorsal  surface;  and  they  gradually  taper  from  their  proximal  ends. 

Bases  or  Upper  Ends. — Their  bases  articulate  with  the  second  row 
of  the  tarsus,  and,  laterally,  with  each  other;  that  of  the  first  excepted. 
The  line  of  the  tarso-metatarsal  articulations  would  be  a  tolerably  even 
curve,  but  for  the  second  metatarsal,  which  is  jammed  into  a  recess  be- 
tween the  cuneiform  bones.  Thus  the  second  metatarsal  is  firmly  locked  in 
like  the  second  metacarpal.  The  bases  of  the  outer  four  slope  outward 

and  backward. 
12 


178  HUMAN   OSTEOLOGY. 

Heads  or  Lower  Ends. — Their  heads,  which  are  much  smaller 
than  those  of  the  metacarpal  bones,  are  convex,  and  fit  into  the  cups  of 
the  first  phalanges;  they  are  grooved  above  for  the  attachment  of  liga- 
ments. 

The  convexity  of  the  head  of  each  metatarsal  extends  downward 
toward  the  sole  of  the  foot — that  is,  in  the  direction  of  flexion — and  ter- 
minates below  in  two  points  called  the  'condyles.'  On  each  side  there  is 
a  tubercle  for  the  attachment  of  the  lateral  ligament.  The  external  con- 
dyle  is  always  the  larger  and  more  prominent,  and  a  well-marked  ridge 
connects  it  with  the  shaft.  Hence,  when  a  metatarsal  bone  is  held  with 
the  head  forward,  and  the  dorsum  of  the  shaft  upward,  the  more  prom- 
inent condyle  will  be  on  the  outer  side. 

First  Metatarsal. — The  excessive  strength  and  size  of  the  first 
metatarsal  bone  which  supports  the  great  toe,  are  peculiar  to  man.  It  is 
the  chief  support  upon  which  the  body  is  raised  by  the  great  muscles  of 
the  calf.  Its  base  presents  a  kidney-shaped  surface,  which  articulates 
exclusively  with  the  internal  cuneiform  bone;  and  there  is  an  impression 


Outer  side.  Inner  side.  Outer  side. 

FIG.  43.— Base  of  First  Right  Metatarsal.          FIGS.  44  and  45.— Base  of  Second  Eight  Metatarsal. 

on  the  outer  side  of  its  plantar  aspect,  indicating  the  insertion  of  the 
'  peroneus  longus '  (Fig.  43).  Its  head  is  remarkably  broad,  and  supports 
the  ball  of  the  great  toe.  It  has  on  its  under  surface  two  grooves  (sepa- 
rated by  a  ridge)  for  the  play  of  the  two  sesamoid  bones. 

Right  or  Left  ? — This  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body  if  he  hold  it  with  the  base  back- 
ward, the  concavity  of  the  kidney-shaped  surface  outward,  and  the  sur- 
face for  the  insertion  of  the  peroneus  longus  downward. 

Second  Metatarsal. — The  second  metatarsal  bone,  the  longest  of 
all,  may  be  known  by  its  triangular  surface  at  the  base  for  the  middle 
cuneiform  bone  (Figs.  44,  45),  a  small  lateral  facet  for  the  inner  cunei- 


THE   METATARSUS 


179 


form,  and  four  lateral  facets  on  its  outer  side;  namely,  two87  for  the  outer 
cuneiform,  and  two  for  the  third  metatarsal  bone.  The  right  may  be 
readily  distinguished  from  the  left  by  attention  to  these  points. 

Third  Metatarsal. — The  third  metatarsal  bone  may  be  known  by 
its  having  two  articular  facets  on  the  inner  side  of  the  base  (Figs.  46, 
47),  and  one  on  the  outer  side. 


Inner  side. 


Outer  side. 


Inner  side. 


Outer  side. 


FIGS.  46  and  47.-Base  of  Third  Right 
Metatarsal. 


FIGS.  48  and  49,— Base  of  Fourth  Right 
Metatarsal. 


Fourth  Metatarsal. — The  fourth  metatarsal  bone  may  be  known 
by  its  square  tarsal  surface  for  the  cuboid,  and  a  single  facet  on  each  side 
(Figs.  48,  49).  The  inner  facet  is,  as  a  rule,  divided  by  a  slight  ridge  into 
an  anterior  and  a  posterior  part;  the  posterior  being  for  the  outer  cunei- 
form. But  the  fourth  metatarsal  does  not  always  touch  the  outer  cune- 
iform. This  variation  is  seen  in  several  speci- 
mens in  the  stores  of  the  Museum  of  the  Royal 
College  of  Surgeons. 

Fifth  Metatarsal.— The  fifth  metatarsal 
bone  can  at  once  be  recognized  by  the  great  pro- 
jection on  the  outer  side  of  its  base.  This  projec- 
tion gives  attachment  to  the  outer  division  of  the 
plantar  fascia,  and  to  the  tendon  of  the  peroneus 
brevis.  The  peroneus  tertius  is  inserted  on  the 
dorsal  aspect  of  the  base.  The  surface  of 
articulation  with  the  cuboid  slants  outward  and 
backward.  There  is  a  round  lateral  facet  for  the  fourth  metatarsal. 

Agreement  between  Metatarsals  and  Metacarpals. — It  may 
be  well  to  remind  the  reader  that  there  is  a  remarkable  agreement  in  the 

8'  These  facets  are  sometimes  joined  so  as  to  form  a  vertical  linear  surface,  but 
generally  the  upper  are  separated  from  the  lower  by  a  gap  for  the  interosseous 
ligament. 


Inner  side.  Outer  side. 

FIGS.  50  and  51.— Base  of  Fifth 
Right  Metatarsal. 


180  HUMAN  OSTEOLOGY. 

majority  of  cases  in  the  number  of  bones  with  which  corresponding  meta- 
tarsals  and  metacarpals  articulate  at  their  bases.  Thus,  the  base  of  the 
first,  in  each  case,  articulates  with  one  bone — that  of  the  second  with 
four — that  of  the  third  with  three — that  of  the  fourth  with  four — and 
that  of  the  fifth  with  two. 

Ossification. — Each  metatarsal  bone  has  two  centres  of  ossification — 
one  for  the  shaft  and  base,  the  other  for  the  head;  excepting  the  metatar- 
sal bone  of  the  great  toe,  which  is  ossified  like  a  phalanx,  that  is  the 
epiphysis  is  at  the  base,  and  thus  it  resembles  the  metacarpal  bone  of 
the  thumb  in  its  development. 

Phalanges  of  the  Toes. — Each  toe  consists  of  three  phalanges, 
excepting  the  great  toe,  which  has  only  two.  The  phalanges  of  the  other 
toes  differ  from  those  of  the  fingers  mainly  in  being  shorter.  To  learn 
the  characters  of  phalanges  the  student  should  refer  to  those  of  the  hand 
as  being  better  marked  than  those  of  the  foot.  The  last  two  phalanges 
of  the  little  toe  are  generally  anchylosed  in  adults,  probably  in  conse- 
quence of  being  cramped  by  tight  shoes.  The  great  toe  is  the  longest  of 
all,  but  in  the  Antique  the  second  is  represented  as  being  the  longest. 

Comparative  Osteology. — Like  the  thumb,  the  first  or  great  toe 
has  only  two  phalanges.  This  is  the  case  throughout  the  whole  mam- 
malian class,  provided  it  supports  a  nail,  a  hoof,  or  a  claw.  The  hind 
foot  of  the  horse  is  the  representative  of  the  third  toe. 


SESAMOID  BONES. 

There  are  two  sesamoid  bones  which  play  in  two  grooves  beneath  the 
head  of  the  first  matatarsal  bone.  They  act  like  little  '  patellae,'  and 
increase  the  leverage  of  the  'muscles  which  work  the  great  toe  (see  p. 
159).  Very  exceptionally  similar  bones  are  met  with  in  the  correspond- 
ing joints  of  other  toes. 

Comparative  Osteology. — There  are  many  sesamoid  bones  in  the 
foot  of  the  great  armadillo  (Priodontes  gigas,  No.  2335  B).  Examine  also 
the  under  surface  of  the  foot  of  the  dog  (No.  4391  A).  There  are  four 
sesamoid  bones  behind  the  pastern  joint  of  the  ox,  and  two  behind  that 
of  the  horse.  The  sesamoid  bone  in  the  tendon  of  the  flexor  longus  digi- 
torum,  behind  the  last  joint,  is  called  by  veterinarians  from  its  shape  the 
'navicular'  bone. 


OBSERVATIONS    ON   THE   FOOT   AS    A   WHOLE.  181 


OBSERVATIONS  ON  THE  FOOT  AS  A  WHOLE. 

General  Observations  on  the  Foot.— The  knowledge  of  the  indi- 
vidual bones  will  be  of  little  practical  use,  unless  the  skeleton  of  the  foot 
be  studied  as  a  whole. 

The  sketch  on  page  182, 88  taken  from  a  preparation,  is  made  to  show 
the  sequence  of  the  bones  which  form  the  inner  and  the  outer  sides  of  the 
longitudinal  arch  of  the  foot.  On  the  inner  side  are  the  astragalus,  the 
scaphoid,  and  the  three  cuneiform  bones  supporting  the  three  inner 
metatarsals.  On  the  outer  side  are  the  os  calcis,  the  cuboid,  and  the  two 
outer  metatarsals.  By  putting  the  two  sides  together,  it  is  easy  to  study 
and  recollect  their  relative  bearings. 

Arches  of  the  Foot. — The  foot  is  a  combination  of  numerous  small 
bones,  so  adapted  and  connected  as  to  form  strong  and,  at  the  same  time, 
elastic  arches. 

Longitudinal  Arch. — The  principal  arch  is  in  the  antero-posterior 
or  long  axis  of  the  foot.  This  '  longitudinal  arch'  has  to  bear  the  weight 
of  the  body  erect.  It  is  supported,  behind,  by  the  tuberosities  of  the  os 
calcis;  and  in  front,  by  the  distal  ends  of  the  metatarsal  bones.  Its  inner 
side  is  much  higher  than  the  outer,  and  is  formed  by  the  astragalus,  the 
scaphoid,  the  three  cuneiform  and  three  inner  metatarsal  bones.  This  is 
well  seen  in  Fig.  52.  The  outer  side  of  the  arch  is  much  lower  than  the 
inner,  and  is  formed  by  the  os  calcis,  the  cuboid,  and  the  two  outer  meta- 
tarsal bones.  It  is  supported  mainly  by  a  strong  ligament  termed  the 
'  calcaneo-cuboid.' 

Transverse  Arch. — Besides  the  longitudinal  arch  there  is  another 
in  the  transverse  direction.  This  is  most  marked  over  the  instep:  that 
is,  its  greatest  convexity  is  across  the  cuneiform  and  the  cuboid  bones. 
Its  inner  side  is  much  thicker  than  the  outer. 

Yielding  of  the  Arches. — When  we  stand,  not  only  does  the  longi- 
tudinal arch  of  the  foot  yield,  but  the  transverse  arch  yields  also.  The 
wedge  bones  and  the  metatarsals  are  connected  by  interosseous  ligaments, 
which,  being  slightly  elastic,  give  a  little,  and  thereby  increase  the  trans- 
verse breadth  of  the  foot.  A  transverse  section  across  the  instep — that 

88  We  are  indebted  for  this  outline  to  Mr.  Keetley,  late  Assistant-Demonstrator  of 
Anatomy  at  St.  Bartholomew's  Hospital. 


182 


HUMAN    OSTEOLOGY. 


is,  through  the  wedge  bones— shows  that  they  are  shaped,  not  like  the 
stones  of  a  bridge,  as  in  Fig.  53,  but  as  represented  in  Fig.  54.     Their 


Os  calcis. 


Cuboid. 


FIG.  52. 


FIG.  53. 


Fio.  54.— Transverse  Section  to  show  the  form 
of  the  Cuneiform  Bones. 


sides  are  not  in  apposition  all  the  way  down,  but  gaps  are  left  between 
them:  now  these  gaps  are  occupied  by  elastic  ligaments,  which  permit  a 


OBSERVATIONS  ON  THE  FOOT  AS  A  WHOLE.  183 

certain  amount  of  separation  between  the  bones  when  the  arch  is  pressed 
upon. 

Mechanism  of  Foot  in  Walking. — Consider  the  mechanism  of 
the  foot  in  the  act  of  walking.  In  standing,  the  weight  of  the  body  is 
transferred  from  the  astragalus  both  backward  and  forward;  backward 
to  the  heel-bone,  forward  to  the  ends  of  the  metatarsals  and  toes.  The 
inner  side  of  the  arch  sinks  a  little;  the  outer  side  touches  the  ground, 
or  nearly  so.  Thus  the  weight  is  evenly  distributed;  the  head  of  the  as- 
tragalus transmitting  it  to  the  inner  side,  the  calcaneum  to  the  outer  side. 
The  foot  then  forms  a  firm  basis  of  support,  becoming  a  little  longer,  and 
a  little  wider  at  the  toes,  owing  to  the  widening  of  the  transverse  arch 
and  the  slight  separation  of  the  metatarsals. 

When  we  begin  to  walk,  the  heel  is  first  raised;  the  astragalus  is 
tilted  forward  and  downward,  but  cannot  slip  off  the  os  calcis  by  reason 
of  the  alternately  convex  and  concave  joints  between  them.  The  astrag- 
alus in  this  position  is  almost  hooked  on  to  the  calcaneum.  It  trans- 
mits the  weight  of  the  body  through  the  scaphoid  to  the  three  inner 
toes,  and  through  the  calcaneum  and  cuboid  to  the  two  outer;  then  the 
weight  is  entirely  sustained  by  the  heads  'of  the  metatarsal  bones,  espe- 
cially that  of  the  great  toe,  which  is  the  last  to  leave  the  ground,  and 
propels  the  body  on  to  the  other  foot,  extended  forward  to  receive  it.89 

Such  is  the  mechanism  of  the  calcaneo-astragaloid  joint.  It  is  equally 
strong  and  transmits  weight  with  the  same  security,  whether  the  pres- 
sure be  vertical,  as  in  the  erect  position,  or  oblique,  as  in  the  middle  of  the 
act  of  walking,  or  when  we  stand  on  tiptoes. 

Our  shoes  ought  to  be  made  so  as  to  permit  the  natural  play  of  the 
arches  of  the  foot.  It  is  manifest  that  the  practice  of  wearing  high  heels 
alters  the  level  of  the  piers  of  the  arches.  By  thus  raising  one  pier,  i.e. 
the  heel  bone,  we  walk  on  an  inclined  plane;  we  alter  the  bearings  of  all 
the  other  bones;  we  throw  the  pressure  on  the  articular  surfaces  of  the 
heads  of  the  metatarsal  bones,  and  thus  give  rise  to  distortion,  crooked 
toes,  bunions  and  corns — local  troubles  which  disincline  or  prevent  us 
from  taking  necessary  exercise,  and  set  up  far  more  serious  constitutional 
ailments. 

Ancient  Egyptian  and  Greek  art  represents  the  second  toe  as  longer 
than  the  great  toe.  This  was  probably  copied  from  the  negro,  for  in  our 

89  For  further  practical  remarks  on  this  subject,  see  '  Anatomy  and  Surgery  of  the 
Human  Foot,'  by  J.  Hancock,  1873. 


184  HUMAN    OSTEOLOGY. 

race  at  the  present  time  the  great  toe  is  certainly  the  longest  of  all  the 
toes  in  the  vast  majority  of  cases.80 

Comparative  Osteology. — The  chief  variations  in  the  digits  of  the 
vertebrata  are  of  number  and  connections.  In  some  instances — e.g.  seal 
(No.  3961),  also  Platanista  Gangetica  (Cetacea,  No.  2482  C) — the  digits 
are  so  bound  together  in  a  common  sheath  that  they  have  little  individ- 
ual movement,  though  they  form  an  excellent  paddle.  The  number  is 
reduced  to  four  in  the  boar  (Nos.  3248-3253  A),  to  three  in  the  rhinoceros 
(No.  2933),  to  two  in  the  ox  (No.  3825  A),  and  to  one  in  the  horse  (No. 
3133,  Equus  Caballus).  The  middle  digit  is  the  most  constant  of  all  the 
digits  in  the  vertebrata.  The  bones  forming  the  three  joints  of  this  toe 
answer  to  those  called  the  '  great  pastern  bone/  the  '  little  pastern  bone/ 
and  the  '  coffin  bone '  in  the  horse,  while  the  nail  in  the  toe  is  represented 
by  the  hoof. 

An  inspection  of  the  separate  series  of  bones  in  the  Osteol.  Mus.  of 
the  Royal  College  of  Surgeons  will  show  that  the  horse  walks  on  his  third 
toe  (i.e.  our  middle  toe),  and  the  pig  and  cow  on  the  third  and  fourth. 
The  kangaroo  walks  on  his  fourth  and  fifth  toes,  the  second  and  third 
being  greatly  diminished  in  size.  Birds  have  three  toes  usually  developed, 
viz.  the  second,  third,  and  fourth;  but  the  ostrich  only  has  two,  viz.  the 
third  and  the  fourth.  The  spur  of  the  cock  is  the  great  toe  nail. 

The  elephant  (Proboscidia,  No.  2654)  has  five  toes,  and  the  weight  of 
the  body  is  supported  by  a  palmar  and  plantar  pad  under  the  toes. 

The  Hyrax  Capensis  (No.  3115  C)  will  be  seen  to  have  four  toes  in 
front,  and  three  behind;  those  in  front  correspond  to  the  second,  third, 
fourth,  and  fifth;  those  behind  to  the  three  middle  ones.  The  inner  nail 
on  the  hind  foot  is  much  curved. 

In  Ungulata  there  are  never  more  than  three  full-sized  toes  on  each 
limb,  and  they  end  in  hoof-like  nails.  They  are  never  plantigrade, 
but  unguligrade,  or  digitigrade. 

A  very  large  number  of  animals,  as  cats,  dogs,  tigers,  and  most  car- 
nivora,  walk  on  their  toes  (digitigrade);  but  bears  may  be  seen  to  have 
five  toes  of  equal  length,  and  to  walk  on  the  flat  of  the  foot — that  is, 
they  bring  the  heel  to  the  ground,  which  makes  them  bad  walkers  but 
good  climbers. 

Tigers  and  cats  can  at  will  either  show  or  hide  their  claws.     When 

90  Professor  Flower,  F.R. S. ,  '  Fashion  in  Deformity, '  p.  67;  also  Professor  Marshall, 
F.R.S.,  'Anatomy  for  Artists,'  p.  45. 


INTEROSSEOUS    MUSCLES    OF    THE    FOOT.  185 

their  claws  are  hidden,  the  ungual  phalanx  with  the  attached  claw  is  bent 
backward  and  on  to  the  outer  side  of  the  second  phalanx  by  a  strong 
elastic  ligament. 

When  these  animals  wish  to  scratch  or  climb  they  set  in  action  the 
flexor  longus  digitorum,  which  flexes  the  ungual  phalanx  and  brings  down 
with  it  the  claw.  Examine  this  beautiful  arrangement  in  the  digit  of  a 
lion,  in  the  comparative  anatomy  of  the  soft  parts  in  the  College  of  Sur- 
geons '  Museum  (No.  287  A). 

Bears  have  not  this  power;  hence  their  claws  are  always  visible,  and 
rattle  on  the  ground  as  they  walk. 

Compare  the  foot  of  the  tiger  with  that  of  the  grizzly  bear. 


INTEROSSEOUS  MUSCLES  OF  THE  FOOT. 

Plan  of  Arrangement. — The  interosseous  muscles  in  the  foot  (Plate 
XXXVII.)  are  arranged  very  much  like  those  in  the  hand.  They  are 
seven  in  number;  four  on  the  dorsal  surface  and  three  on  the  plantar. 
Observe  that  the  dorsal  arise  from  the  opposite  side  of  the  metatarsal 
bones,  and  are  inserted  into  the  first  phalanges  of  the  second,  third,  and 
fourth  toes,  so  that  they  draw  the  toes  from  a  line  corresponding  to  the 
axis  of  the  second  toe.  It  should  be  remembered  that,  in  the  case  of  the 
hand,  this  line  corresponds  to  the  axis  of  the  middle  finger. 

The  plantar  belong  to  the  three  outer  toes;  each  arises  from  one 
metatarsal  bone,  and  is  inserted  into  the  first  phalanx  of  the  same  toe  on 
the  inner  side  of  its  base,  so  that  they  draw  toward  the  above-mentioned 
line. 


THE  THOKAX. 

(PLATES  XXXIX.  TO  XLII.) 

General  Description. — The  thorax  is  the  framework  which  contains 
the  heart  and  lungs.  The  ribs,  with  their  cartilages,  describe  a  series  of 
arcs,  successively  increasing  in  length  as  far  as  the  seventh,  and  form, 
with  the  spine  and  sternum,  a  barrel  of  a  somewhat  conical  shape,  much 
broader  from  side  to  side  than  from  before  backward.  The  lower  aperture 
or  base  of  the  cavity  is  open  in  the  skeleton,  but  closed  in  the  recent  sub- 
ject by  a  thin  flat  muscle,  called  the  '  diaphragm/  which  separates  the  chest 
from  the  abdomen,  and  has  openings  for  the  passage  of  the  alimentary 
canal  and  the  great  blood-vessels.  This  muscular  partition  is  not  flat  but 
arched,  so  that  it  forms  a  vaulted  floor  for  the  chest.  By  alternately 
falling  and  rising,  it  increases  and  diminishes  the  capacity  of  the  chest. 
The  spaces  between  the  ribs  are  filled  by  the  intercostal  muscles.  In  each 
space  there  are  two  layers  which  cross  like  the  letter  X:  the  outer  layer 
runs  downward  and  forward:  the  inner,  upward  and  forward. 

Such,  in  outline,  is  the  framework  of  the  chest.  Its  walls  are  made 
up  of  different  structures — bones,  cartilages,  and  muscles,  which  by  their 
union  answer  two  apparently  incompatible  purposes.  By  their  solidity 
and  elasticity  they  protect  the  important  organs  contained  in  the  chest; 
and  by  alternately  dilating  and  contracting,  serve  as  the  mechanical  agents 
of  respiration.  They  enlarge  the  cavity  of  the  chest  in  three  directions: 
in  height,  by  the  descent  of  the  diaphragm;  in  width,  by  the  turning 
outward  of  the  ribs;  in  depth,  by  the  raising  of  the  sternum. 


THE  STERNUM. 
(PLATE  XXXIX.) 

Position. — The  sternum  (arspvov,  the  breast)  is  a  long  flat  bone,  situ- 
ated in  front  of  the  chest,  and  supports  the  ribs  and  the  clavicles.  In  the 
adult  male,  it  is  from  six  to  seven  inches  long:  rather  less  in  the  female. 


PLATE  XXXIX. 


THE    STERNUM.  187 

Observe  that  its  direction  is  not  perpendicular,  but  that  it  slants  forward, 
and  thus  makes  more  room  for  the  heart  and  lungs.  It  is  much  broader 
and  thicker  at  the  upper  end  (manubrium),  where  it  supports  the  clavi- 
cles. The  sternum  was  compared  by  the  ancients  to  a  sword;  the  broad 
part  was  called  'manubrium,'  the  middle  part  'mucro/  and  the  cartilage 
at  the  end  the  '  xiphoid '  or  '  ensif orm '  cartilage. 

Transverse  Lines  and  Manubrium.— We  notice  upon  the  ster- 
num four  faintly-marked  transverse  lines,  which  are  traces  of  the  original 
division  of  the  bone  into  five  pieces.  The  most  conspicuous  of  these  lines 
corresponds  with  the  insertion  of  the  second  costal  cartilage;  that  is,  at 
the  junction  of  the  manubrium  with  the  second  piece.  This  line,  easily 
felt  in  the  living  subject,  has  the  second  costal  cartilage  at  each  end  of 
it.  The  '  manubrium '  or  '  presternum '  has  a  notch  on  the  top  (inter- 
clavicular  notch),  on  either  side  of  which  is  an  oblong  articular  surface 
for  the  clavicle.  In  the  dry  bone,  this  surface  is  flat;  but  in  the  recent 
state,  the  incrusting  cartilage  makes  it  somewhat  saddle-shaped;  that  is, 
concavo-convex.  This  kind  of  joint  permits  the  clavicle  to  rotate  nearly 
as  freely  as  the  thumb  does  on  the  trapezium.  The  end  of  the  clavicle  is 
much  larger  than  the  surface  on  which  it  rotates,  yet  dislocation  of  it  is 
exceedingly  rare,  owing  to  the  great  strength  of  the  ligaments.  To  break 
the  clavicle  is  much  easier  than  to  dislocate  it. 

Mesosternum  and  Notches. — Each  border  of  the  middle  division 
of  the  sternum  ('mesosternum')  has  six  notches  in  it,  which  receive  the 
cartilages  of  six  of  the  true  ribs.  All  the  notches,  except  that  for  the 
first  rib,  are  situated  where  the  original  pieces  of  the  bone  unite.  In 
some  instances  there  is  a  hole  in  its  lower  part. 

Ensiform  Cartilage. — The  ensif  orm  cartilage  (or  *  xiphisternum ') 
at  the  lower  end  of  the  sternum  generally  remains  unossified,  even  at  a 
great  age.  Its  length  and  shape  vary  much  in  different  persons.  Some- 
times it  is  bent  forward,  or,  it  may  be,  backward,  and  this  especially  in 
workmen  who  hold  tools  against  the  pit  of  their  stomach.  Occasionally  it 
is  forked  at  the  end.  It  gives  attachment  to  a  narrow  aponeurotic  band, 
termed  the  'linea  alba,' which  descends  along  the  middle  line  of  the 
abdomen  to  the  symphysis  pubis,  and  is  the  fibrous  continuation  of  the 
sternum. 

The  anterior  surface  of  the  sternum  gives  origin  to  the  'sterno- 
mastoid '  and  the  '  pectoralis  major/  The  posterior  surface  gives  origin 
to  the  '  sterno-hyoid '  and  '  sterno-thyroid '  and  to  the  '  triangularissterni/ 


188  HUMAN  OSTEOLOGY. 

The  posterior  surface  of  the  ensiform  cartilage  gives  Origin  to  the  '  dia- 
phragm.' 

Ossification. — Until  the  middle  of  foetal  life,  the  sternum  is  entirely 
cartilaginous.  It  is  ossified  from  five  centres,91  not  simultaneously,  but 
successively  from  above  downward,  opposite  the  intercostal  spaces.  The 
five  bones,  thus  formed,  ultimately  coalesce,  the  lower  first,  and  so  on 
upward — the  reverse  of  the  order  in  which  they  were  ossified.  Thus  the 
fifth  unites  to  the  fourth  about  puberty;  the  fourth  to  the  third  about 
the  age  of  twenty  or  twenty-five;  the  third  to  the  second  about  thirty- 
five  or  forty;  the  second  rarely  unites  to  the  first,  or,  if  so,  only  in  ad- 
vanced age;  and  even  then  there  is  only  a  thin  layer  of  bone  externally; 
the  cartilage  in  the  centre  still  remains.  The  first  and  second  bones  of 
the  sternum  remain  ununited  on  account  of  a  certain  amount  of  motion 
between  them  during  respiration.  In  some  subjects  the  line  of  articu- 
lation is  very  perceptible  through  the  skin,  more  especially  in  persons 
emaciated  by  disease.  It  corresponds  with  the  middle  of  the  second  costal 
cartilage. 

Comparative  Osteology. — Contrast  the  broad  chest  of  man  with 
that  of  the  ourang  outan  (No.  5050)  and  that  of  the  chimpanzee  (Xos. 
5082-5083  A  and  B).  In  the  adult  gorilla  the  parts  of  the  sternum, 
which  in  us  are  united,  are  seen  to  remain  separate. 

In  the  Separate  Series,  as  well  as  in  the  two  complete  skeletons  in  the 
Normal  Human  Osteological  Series,  examine  the  sternum  of  the  Bush- 
man and  you  will  see  that  the  manubrium  sterni  is  firmly  united  to  the 
gladiolus,  and  there  is  little  or  no  trace  of  the  original  separations  be- 
tween the  pieces  of  which  the  sternum  is  composed. 

Most  flying  animals  support  themselves  in  the  air  by  the  action  of 
their  pectoralis  major  muscle  on  the  upper  extremity,  and  therefore  this 
muscle  is  large  in  proportion  with  the  flying  capability.  The  surface  of 
origin  in  such  animals  is  increased  by  the  development  of  a  great  keel 
down  the  middle  of  the  sternum,  which  may  be  seen  in  any  of  the  flying 
birds  (Carinatce),  for  instance,  in  the  great  bustard  (No.  1349),  as  well 

"  Exceptions  to  this  rule  are  frequent.  There  may  be  two,  three,  or  more  centres 
for  the  first  bone;  and,  instead  of  a  single  centre,  any  of  the  other  pieces  may  have 
two,  placed  side  by  side.  The  sternum  is  formed  in  cartilage  along  the  line  where 
the  '  ventral  lamina?' of  early  embryonic  life  unite.  Partial  failure  of  this  union 
accounts  for  the  longitudinal  cleft  occasionally  seen  in  the  body  of  the  human 
sternum;  and  the  appearance  of  symmetrical  points  of  ossification  is  explained  in  the 
same  manner. 


THE    RIBS.  189 

as  in  the  extinct  flying  lizards  (Pterosauria,  No.  A  119,  Pal.  Ser.  Mus. 
Roy.  Coll.  Surg.).  This  keel  is  absent  in  the  non-flying  birds,  such  as 
the  ostrich  (No.  1362),  the  extinct  dinomis  (No.  1588  A,  Pal.  Ser.  Roy. 
Coll.  Mus.  Surg.),  the  apteryx  (Nos.  1355  and  1355  E),  showing  that  this 
keel  exists  for  the  function  of  flight  and  not  as  a  class  character  of  aves. 

Among  the  variations  which  the  sternum  undergoes  perhaps  the  most 
curious  is  that  in  the  male  wild  swan  and  guinea-fowl  (see  Nos.  1248  B, 
1249  A,  B,  C),  where  it  will  be  seen  to  be  tunnelled  extensively,  and  to 
contain  a  long  tortuous  trachea  as  well  as  the  inferior  larynx. 

The  front  part  of  the  case  of  the  turtle  is  formed  by  the  expanded 
sternum,  while  the  back  part  is  formed  by  the  consolidation  of  the  ribs 
and  expansion  of  the  spines  of  the  dorsal  vertebrae  (No.  961  A,  snapping 
turtle). 

In  snakes  (Ophidia)  there  is  neither  a  sternum  nor  a  pectoral  arch 
(Xo.  629),  and  there  is  no  trace  of  a  fore  limb. 

There  is  no  sternum  either  in  ichthyosauria  or  plesiosauria  (Nos.  172 
and  222  Palaeontological  Series,  Mus.  Roy.  Coll.  Surg.). 


THE  RIBS. 
(PLATE  XXXIX.) 

Number  and  Division. — There  are  twelve  ribs  on  each  side;  the 
upper  seven,  the  '  sternal/  or  '  true  ribs/  increase  in  length  from  the  first, 
and  are  fixed  to  the  sternum  by  their  cartilages.  The  lower  five,  or  '  false 
ribs/  decrease  in  length  from  above  downward,  and  their  cartilages  fall 
short  of  the  sternum.  The  cartilages  of  the  eighth,  ninth,  and  tenth  ribs 
are  connected  to  that  of  the  seventh.  The  eleventh  and  twelfth  are  free, 
and  are  therefore  called  '  floating  ribs/  One  sometimes,  though  rarely, 
meets  with  skeletons  with  thirteen  ribs,  the  thirteenth  being  a  lumbar 
rib.  This  is  a  retrocession.  The  chimpanzee  has  thirteen  ribs,  but  the 
same  number  of  vertebrae  as  man. 

General  Characters  of  a  Rib. — As  an  example  of  the  general  char- 
acters of  a  rib,  take  the  fifth  or  sixth.  In  the  first  place,  observe  that, 
the  curve  is  not  uniform.  It  is  more  curved  toward  the  vertebral  end 
than  elsewhere.  Besides  which,  if  laid  on  a  table,  the  vertebral  end  will 


190  HUMAN    OSTEOLOGY. 

rise.  It  is  plain  in  the  skeleton  that  the  vertebral  ends  of  the  ribs  are 
higher  than  the  sternal  ends.  If  both  ends  had  been  on  the  same  level, 
the  sternum  could  not  have  been  raised  forward  in  inspiration. 

Vertebral  End.— The  vertebral  end  or  'head'  (Plate  XXXIX.  Fig. 
3)  has  two  oblique  surfaces  (with  an  intervening  ridge,  to  which  the 
interarticular  ligament  is  attached),  which  articulate  with  the  sides  of 
the  bodies  of  two  contiguous  vertebrae.  The  lower  of  these  two  surfaces 
is  always  the  larger.  The  head  of  the  rib  is  the  fulcrum  upon  which  the 
rib  moves.  It  is  wedged  in  between  two  vertebras,  and  is  less  liable  to  be 
dislocated  than  if  supported  by  one  only;  and,  moreover,  it  has  the 
benefit  of  the  elasticity  of  the  intervening  fibro-cartilage.  This,  as  Paley 
observes,  is  '  the  very  contrivance  employed  in  the  famous  iron  bridge  at 
Bishop's  Wearmouth/ 

Neck. — Next  to  the  head  comes  the  'neck'  of  the  rib.  This  is 
smooth  in  front,  where  it  is  covered  by  pleura, 
but  rough  behind,  where  is  attached  a  liga- 
ment (middle  costo-transverse)  connecting  it 
to  the  transverse  process  by  which  the  rib  is 
supported,  as  seen  in  the  adjoining  figure; 

FIG.  55,-Dorsal  Vertebra  with      again>    the   neck    haS    a    ridg6   along    its   UPP61' 

surface  to  which  is  attached  a  second  liga- 
ment (superior  costo-transverse);  this  connects  it  to  the  transverse  pro- 
cess above  it. 

Tubercle. — External  to  the  neck  is  the  '  tubercle.'  It  has  a  little 
facet  which  looks  downward  and  articulates  with  the  transverse  process 
supporting  the  rib;  in  front  and  rather  above  the  facet  is  the  rougher 
part  of  the  tubercle  which  gives  attachment  to  a  third  ligament  connect- 
ing the  rib  to  the  transverse  process  (posterior  costo-transverse). 

Angle. — External  to  the  tubercle,  the  rib  makes  a  curve  forward, 
forming  the  '  angle.'  Here  there  is  a  prominent  line  which  runs  obliquely 
downward  and  forward,  and  indicates  the  attachment  of  muscles,  which 
form  the  outer  border  of  the  '  erector  spinae.'  Observe  that  the  distance 
between  the  angle  and  the  tubercle  increases  as  we  trace  the  ribs  down- 
ward, and  makes  room  for  the  great  muscle  of  the  spine  (erector  spinae). 
It  is  near  the  angle  that  the  rib  breaks  when  the  chest  is  compressed, 
for  instance,  in  a  crowd.  In  this  kind  of  fracture — i.e.  by  indirect 
violence — the  broken  ends  project  outward,  and  are  therefore  less  liable 
to  injure  the  pleura.  But  in  direct  violence — e.g.  a  kick  by  a  horse — the 


THE    RIBS.  191 

rib  breaks  where  it  is  struck,  the  broken  ends  are  driven  inward,  and 
consequently  are  more  liable  to  injure  the  pleura. 

Shaft. — The  rest  of  the  rib  arching  forward  from  the  angle  along  the 
side  of  the  chest  is  called  the  '  shaft.'  It  is  flattened  from  above  down- 
ward, like  a  bow.  On  its  inner  surface,  near  the  lower  border,  is  a  deep 
groove  for  the  intercostal  vessels  and  nerve.  Observe,  the  groove  does  not 
extend  the  whole  length  of  the  rib:  it  begins  about  the  angle,  and  is 
gradually  lost  before  we  come  to  the  anterior  end.  The  vessels  and  nerves 
are  safe  where  they  lie  in  the  groove;  but  between  the  angle  of  the  rib  and 
the  spine,  and  again  in  front  of  the  chest,  they  are  liable  to  be  injured 
through  the  intercostal  spaces.  In  consequence  of  this  groove,  the  lower 
edge  of  the  rib  is  much  thinner  than  the  upper,  which  is  thick  and 
rounded.  In  the  groove  itself  are  the  orifices  of  the  numerous  canals 
which  transmit  blood-vessels  into  the  interior  of  the  rib.  The  ribs  are 
the  most  vascular  bones  in  the  body:  hence  the  rapidity  with  which  they 
unite  after  a  fracture.. 

Anterior  End. — Respecting  the  anterior  end,  remark  that  it  is 
rough,  and  a  little  excavated  to  receive  the  costal  cartilage. 

Right  or  Left  ? — A  rib  will  be  in  the  same  position  as  the  corre- 
sponding one  in  the  student's  body  if  he  hold  the  convex  surface  outward, 
the  head  backward,  and  the  groove  downward.  In  distinguishing  right 
from  left  ribs  it  should  be  borne  in  mind  that  the  articular  facet  for  the 
transverse  process  looks  downward  in  every  case. 

Peculiarities  of  certain  Ribs. — The  first,  second,  tenth,  eleventh, 
and  twelfth  ribs  have  peculiarities  requiring  separate  notice. 

First  Rib. — The  plane  of  the  first  rib  is  nearly  horizontal.  It  is  the 
shortest,  the  most  curved,  the  flattest  and  broadest  of  all.  Its  head  has 
a  single  articular  surface  which  rests  on  the  first  dorsal  vertebra.  It  has 
the  largest  tubercle,  and  this  is  well  supported  by  the  strong  transverse 
process  of  the  first  dorsal  vertebra.  There  is  scarcely  a  trace  of  angle. 
On  its  upper  surface  we  may  see  in  a  well-marked  bone  two  slight  trans- 
verse grooves  about  the  breadth  of  a  finger;  the  subclavian  artery  lies  in 
the  posterior  groove  as  it  crosses  the  rib,  the  vein  passes  along  the  ante- 
rior. Against  this  surface  the  subclavian  artery  may  be  effectually  com- 
pressed. The  grooves  are  separated  on  the  inner  border  of  the  rib  by  a 
'  tubercle'  denoting  the  insertion  of  the  '  scalenus  anticus.'  Behind  this 
is  the  rough  surface  for  the  insertion  of  the  *  scalenus  medius.'  Lastly, 
there  is  no  groove  for  the  intercostal  artery. 


192  HUMAN    OSTEOLOGY. 

It  is  an  interesting  fact,  that  the  compact  tissue  forming  the  concave 
margin  of  the  first  rib  is  very  much  thicker  than  that  on  the  convex  side. 
The  first  rib  is  the  strongest  of  all:  it  has  to  support  the  manubrium 
sterni  and  the  clavicles,  and  to  protect  all  the  important  parts  at  the  base 
of  the  neck.  The  first  rib  is  very  rarely  fractured,  being  so  well  protected 
by  the  clavicle;  but  when  it  does  happen  it  is  a  most  serious  accident, 
because  it  is  the  starting  point  of  all  the  other  ribs  in  respiration,  and  be- 
cause there  are  so  many  important  vessels  and  nerves  in  relation  with  it. 

Second  Rib. — The  second  rib  has  little  or  no  angle,  no  twist  on  its 
axis,  and  has,  near  the  middle  of  its  outer  surface,  a  rough  eminence  for 
the  origin  of  the  second  and  third  digitations  of  the  serratus  magnus.  It 
has  a  short  groove  for  the  intercostal  artery. 

Tenth  Rib. — The  tenth  rib  has  a  single  '  facet '  on  the  head,  for  the 
tenth  dorsal  vertebra. 

Eleventh  and  Twelfth  Ribs. — The  eleventh  and  twelfth  ribs  being 
shorter  and  less  perfectly  developed,  are  chiefly  distinguished  by  their 
negative  characters.  Each  articulates  with  only  one  vertebra,  so  that  the 
head  has  only  one  facet,  does  not  touch  the  transverse  process,  and  has 
no  tubercle.  Each  is  tipped  with  cartilage.  The  eleventh  has  a  trace 
of  an  angle  and  a  groove.  In  the  twelfth,  angle  and  groove  are  imper- 
ceptible. 

Ossification. — Ossification  in  the  ribs  begins  about  the  seventh  week 
of  fcetal  life.  There  is  one  '  primary  *  centre  for  the  body,  an  epiphysis 
for  the  head,  and  another  for  the  tubercle.  The  epiphyses  appear  from 
the  fifteenth  to  the  eighteenth  year,  and  unite  with  the  rest  of  the  bone 
about  the  age  of  maturity. 

Costal  Cartilages. — Respecting  the  costal  cartilages,  remember  that 
the  first  seven  are  connected  with  the  sternum.  The  first  cartilage  is 
united  directly  with  the  manubrium.  The  others,  from  the  second  to 
the  seventh  inclusive,  are  articulated  to  the  sternum  with  the  intervention 
of  synovial  membranes  which  disappear  in  old  age.  The  cartilages  of  the 
eighth,  ninth,  and  tsnth  ribs  are  gradually  bevelled  off,  and  each  joins 
the  costal  cartilage  immediately  above  it.  Moreover,  synovial  membranes 
exist  between  these  last-mentioned  ribs.  The  last  two  costal  cartilages 
do  not  join  those  above,  but  merely  cap  the  eleventh  and  twelfth  ribs. 
These  numerous  little  articulations,  connected  with  the  cartilages,  much 
facilitate  the  respiratory  movements  of  the  thorax. 

The  costal  cartilages  increase  in  length  from  above,  and  allow  the 


PLATE  XLI. 


C 


1s.  Lumbar  vei-tr:bra 


THE    RIBS.  193 

requisite  play  of  the  ribs  in  respiration.  Their  great  elasticity  answers  two 
purposes.  1.  They  act  as  mechanical  agents  of  expiration  by  depressing 
the  ribs  after  they  have  been  raised  by  muscular  action.  2.  A  blow  on 
the  sternum  is  distributed  over  fourteen  elastic  arches!  One  can  under- 
stand, then,  why  the  ch^st  is  able  to  bear  such  tremendous  blows  with 
impunity;  more  especially  during  a  full  inspiration.  During  expiration 
the  bones  are  less  able  to  resist  injury,  because  the  muscles  are  not  acting. 
Notwithstanding  these  beautiful  provisions,  the  sternum  is  sometimes 
broken,  especially  when  the  cartilages  of  the  ribs  are  ossified.  Dupuytren 
mentions  the  case  of  a  fireman  whose  sternum  was  broken  by  the  fall  of 
a  piece  of  timber.  The  man  was  carried  away,  supposed  to  be  dead. 
Coming  up  accidentally,  Dupuytren  replaced  the  sternum,  and  the  man 
recovered. 

Thorax  as  a  Whole. — In  addition  to  what  has  been  said  of  the 
thorax  at  p.  186,  attention  should  be  directed  to  one  or  two  points  which 
might  otherwise  be  overlooked.  1.  The  great  narrowness  of  the  upper 
opening  of  the  chest.  In  an  adult  of  average  size,  it  measures  about  2 
inches  from  before  backward,  and  3£  inches  transversely.  Yet  in  this 
seemingly  narrow  space  there  is  room  for  the  trachea,  the  oesophagus,  the 
great  blood-vessels  and  nerves  at  the  root  of  the  neck,  besides  the  apex 
of  each  lung,  and  three  muscles  on  each  side.  2.  Notice  how  much  the 
ribs  slope  in  subserviency  to  the  mechanism  of  respiration.  Their  sternal 
and  vertebral  ends  are  not  in  the  same  horizontal  plane;  for  instance,  the 
sternal  end  of  the  third  rib  is  not  oh  a  level  with  the  third  dorsal  verte- 
bra, but,  roughly  speaking,  with  the  sixth.  3.  Notice  how  much  addi- 
tional space  is  gained  posteriorly  (for  the  lungs)  by  the  backward  projec- 
tion of  the  ribs.  4.  Notice  that  the  lower  margin  of  the  thorax  is  rep- 
resented by  a  line  sloping  from  the  end  of  the  sternum  downward  and 
backward  to  the  last  rib.  5.  Notice  that  the  intercostal  spaces  are  widest 
where  the  ribs  unite  to  their  cartilages;  and  narrowest  where  the  ribs 
join  the  spine. 

Mechanism  of  Inspiration. — It  is  proposed  to  explain  now  how 
the  chest  is  enlarged  in  the  transverse  and  in  the  antero-posterior  direc- 
tion by  the  elevation  of  the  ribs. 

The  spine  is  fixed,  and  serves  as  a  fulcrum  for  the  ribs,  which  are  the 
levers. 

At  the  moment  of  inspiration,  the  ribs,  which  you  must  remember  are 

oblique,  are  raised  by  the  intercostal  muscles.     The  centre  of  motion 
13 


194 


HUMAN    OSTEOLOGY. 


being  at  the  spine,  it  is  plain  that  the  more  nearly  the  ribs  become  hori- 
zontal, the  greater  will  be  the  distance  between  the  spine  and  the  sternum. 
Thus,  let  the  line  VV,  in  Fig.  56,  represent  the  spine;  the  line  SS  the 
sternum;  a,  b,  c,  three  ribs  in  their  oblique  position;  and  a'}  V ,  c',  the  same 
ribs  elevated.  It  is  obvious  that  by  raising  th$  ribs  we  increase  at  the 
same  time  the  antero-posterior  diameter  of  the  chest;  or,  in  other  words, 
we  increase  the  distance  between  the  spine  VV  and  the  sternum  SS. 
The  same  diagram  proves  that,  when  the  ribs  are  raised,  the  intercos- 


FIG.  56. 


tal  spaces  are  widened;  that  is,  a  perpendicular  let  fall  between  two  ribs  is 
longer  when  the  ribs  are  raised  than  when  they  are  depressed. 

Now,  when  the  ribs  rise,  they  describe  a  rotatory  movement  around 
an  imaginary  axis,  as  shown  at  A  B,  Fig.  57,  which  unites  their  vertebral 
and  sternal  ends.  In  consequence  of  this  rotation  on  its  ends,  the  exter- 
nal surface  of  the  rib,  which  looks  downward  and  outward  when  at  rest, 
looks  directly  oiitward  when  raised.  Thus  the  transverse,  diameter  of  the 
chest  is  increased. 

If  the  ribs  were  all  of  the  same  length,  as  in  Fig.  56,  the  projection  of 
the  sternum,  caused  by  their  elevation,  would  be  equal  all  the  way  down. 
But  since  the  lower  sternal  ribs  are  longer  than  the  upper,  it  follows  that 
the  sternum  is  projected  in  inspiration  more  and  more  toward  its  lower 
end. 

The  ribs  are  raised  by  the  external  intercostal  muscles  (which  run 


THE    RIBS. 


195 


obliquely  downward  and  forward);  they  are  depressed  by  the  internal 
intercostal  muscles  (which  run  obliquely  upward  and  forward).  These 
facts  are  rendered  probable  (if  not  absolutely  proved)  by  the  following 
diagram: — 


Let  V  V  represent  the  spine,  1'  2'  two  ribs  in  a  state  of  obliquity  or 
rest,  and  a'  a  fibre  of  an  external  intercostal  muscle.  Now,  when  the 
fibre  a'  contracts,  it  shortens  itself:  but  this  shortening  cannot  take  place 
unless  the  ribs  are  at  the  same  time  brought  more  into  the  horizontal  line, 
as  shown  at  1,  2;  in  other  words,  unless  they  are  raised;  therefore  the 
external  intercostal  muscles  are  inspiratory  muscles. 

The  same  kind  of  demonstration  proves  that  the  internal  intercostal 
muscles  depress  the  ribs,  and  are  therefore  expiratory  muscles.  For  let 
b  be  a  fibre  of  an  internal  intercostal  muscle  extended  between  the  ribs 
3  and  4  in  a  state  of  elevation,  it  is  easy  to  see  that,  when  the  fibre  b  con- 
tracts or  shortens  itself,  it  cannot  do  so  without  bringing  the  ribs  into  a 
more  oblique  position,  as  shown  at  3'  and  4'.  That  the  fibre  V  must  be 
shorter  than  the  fibre  b  may  be  proved  by  a  pair  of  compasses. 

Comparative  Osteology. — It  is  curious  that  the  gorilla  and  chim- 
panzee have  each  13  pairs  of  ribs.  So  that  man  in  his  descent  from  his 
pretended  ancestors  must  have  lost  a  rib,  for  he  (like  the  man  of  the 
woods,  orang  outan)  has  only  12. 

In  mammalia  the  number  of  ribs  on  each  side  ranges  from  9  in  the 
bottle-nosed  whale  (Hyperoodon,  No.  2479),  to  24  in  the  two-toed  sloth 


196  HUMAN    OSTEOLOGY. 

(No.  2387  A).  The  horse  and  tapir  have  18  pairs  each,  and  the  ele- 
phant 19. 

The  ribs  of  the  manatee  (No.  2647  A)  are  extraordinarily  thick,  broad, 
and  massive. 

In  whales  some  of  the  posterior  ribs  are  attached  only  to  the  trans- 
verse processes  of  the  vertebrae.  Commonly  in  mammalia  about  6  ribs 
articulate  with  the  sternum  by  cartilage  or  bone,  but  in  whales  the  num- 
ber so  attached  is  much  smaller,  in  the  whale-bone  whale  there  being  only 
one  pair  of  true  ribs. 

This  freedom  of  action  allows  the  great  play  of  the  respiratory  appa- 
ratus in  cetacea. 

Some  animals  have  the  costal  cartilages  ossified,  forming  sternal  ribs, 
as  in  the  giraffe,  crocodile,  ox,  porpoise,  and  dolphin;  in  many  there  is 
an  intermediate  rib,  or  shaft  of  bone,  set  in  between  the  sternal  and  ver- 
tebral ribs  (see  Nilotic  crocodile,  No.  717  D,  and  monotremata,  No.  1698). 

The  ribs  are  mostly  used  solely  for  respiration  throughout  the  animal 
kingdom.  In  addition  to  this  the  snakes  use  the  tips  of  them  to  walk 
upon,  and  the  flying  lizard  (Draco  volans,  No.  673)  has  the  5  posterior 
ribs  so  recurvated  and  elongated  as  to  form  the  bony  skeleton  of  the 
membranous  sail  by  which  he  supports  himself  in  his  flight  from  tree  to 
tree. 

The  middle  part  of  the  ribs  in  birds  (see  griffin  vulture,  No.  1674) 
presents  a  long  flat  process  which  projects  backward  and  rests  on  the  rib 
below.  These  are  called  uncinate  processes. 

There  are  no  processes  in  mammalia  corresponding  to  the  uncinate 
processes  in  birds.  They  are,  however,  seen  in  alligators  (No.  760  A). 

Sharks  and  rays  have  no  ribs.  What  appear  to  be  ribs  in  the  Por- 
beagle shark  (No.  419  A)  are  simply  the  supports  of  the  gills,  as  may  be 
understood  bv  a  reference  to  the  skeleton  of  the  cod-fish  (No.  147  A), 
which  has  17  pairs  of  ribs.  The  Alausa  tyrannus  (No.  39  A)  has  not 
only  many  ribs,  but  a  good  sternum. 

Examine  the  great  Nilotic  crocodile  (No.  717  D),  and  you  will  see 
that  an  anterior  and  a  posterior  bar  forming  the  transverse  processes  of 
the  cervical  vertebrae  correspond  to  the  two  processes  which  in  the  dorsal 
vertebras  support  respectively  the  head  and  the  tubercle  of  the  rib.  In 
its  middle  and  posterior  dorsal  regions  the  end  of  a  transverse  process 
supports  both  the  head  and  the  tubercle  of  the  rib.  There  will  be  seen 
also  what  are  called  intermediate  ribs,  i.e.  a  piece  of  bone  between  the 


THE    RIBS.  197 

end  of  the  rib  and  the  costal  cartilage  or  sternal  rib.  Some  of  the  ribs 
are  furnished  with  nncinate  processes  as  in  birds;  but  this  is  better  seen 
iu  the  alligator  (No.  760  A).  Seven  pairs  of  false  ribs  are  developed  as 
superficial  ossifications  of  the  linese  transversae  in  the  abdominal  wall  (see 
also  No.  711  A). 

The  extinct  flying  lizards,  Pterosauria  (No.  119  A),  had  splint-like 
sternal,  as  well  as  abdominal,  ribs. 

In  Ophidia  (No.  630)  the  ribs  articulate  only  with  the  ends  of  trans- 
verse processes. 


MUSCLES  OF  THE  BACK. 

(PLATES  XLII.  TO  XL VIII.) 

IiT  the  description  of  the  muscles  of  the  back  the  more  superficial 
muscles,  connected  with  the  arm,  will  be  first  considered.  These  re- 
moved, the  great  muscles  of  the  spine,  which  fill  up  the  vertebral  grooves, 
and  keep  the  body  erect,  are  exposed.  Lastly,  there  is  the  mass  of 
muscles  at  the  back  of  the  neck  attached  to  the  occipital  bone. 


THE  SUPERFICIAL  MUSCLES  OF  THE  BACK. 

These  are  shown  in  Plate  XLII.  The  most  superficial  is  the  '  tra- 
pezius/ a  triangular  muscle  of  which  the  limits  are  defined  by  the  con- 
tinuous dark  line.  The  other  wide-spreading  superficial  muscle  is  the 
'  latissimus  dorsi/  Under  the  trapezius  we  have  the  '  rhomboidei '  and 
the  '  levator  anguli  scapulae  '  shown  in  Plate  XLIV. 

"  0.  Occiput;   ligamentum  nuchas:    spines  of 

all  the  dorsal  vertebrae. 
Trapezius       .        .        .  <  T    _  . 

I.  Spine  of  scapula;  acromion,  acromial  third 

of  clavicle. 

0.  Crest  of  the  ilium.    Spines  of  all  the  lum- 

bar, and  six  lower  dorsal  vertebras,  and 
Latissimus  dorsi     .        .  •<          ,     _.  .,  ,.        .        ,.     ,. 

by  digitations  from  the  three  lower  ribs. 

1.  Bottom  of  bicipital  groove  of  humerus. 

,   (  0.  Spines  of  last  cervical   and  five   upper 
Ehomboideus  (manor  and 

•<  dorsal  vertebras. 

I  I.  Posterior  border  of  scapula. 

0.  Transverse  processes  (posterior  tubercles) 
Levator  anguli  scapulas  .  \          of  four  upper  cervical  vertebras. 

1.  Upper  angle  of  scapula. 


PLATE  XLli:. 


PLATE  XL1V 


THE  SUPERFICIAL  MUSCLES  OF  THE  BACK. 


199 


200  HUMAN    OSTEOLOGY. 

The  *  intertransversales '  pass  between  the  transverse  processes  of  con- 
tiguous vertebrae,  the  '  interspinales '  between  the  spinous  processes  be- 
ginning at  the  axis.  Both  these  sets  are  ill  developed  and  mostly  tendi- 
nous in  the  dorsal  region. 

The  '  transverso-spinalis '  is  the  mass  which  fills  up  the  space  between 
the  transverse  and  spinous  process  of  the  vertebra.  It  arises  from 
transverse,  and  is  inserted  into  spinous  processes.  Therefore  its  direc- 
tion is  oblique.  It  is  composed  of  several  bundles.  The  more  super- 
ficial pass  over  many  vertebrae;  the  deeper  over  one  or  two;  the  deepest 
run  from  vertebra  to  vertebra.  The  '  transverso-spinalis '  comprises  the 
'  semi-spinalis-dorsi/  '  semi-spinalis  colli/  '  multifidus  spinge/  and  '  rota- 
tores  spinae '  of  systematic  authors. 

The  '  levatores  costarum '  arise  from  the  transverse  processes,  and  are 
inserted  into  the  ribs  below  them. 


MUSCLES  OF  THE  BACK  OF   THE  NECK. 
(PLATE  XLV.) 

A  separate  group  is  made  of  these,  because  they  specially  maintain  the 
head  erect,  and  move  the  first  upon  the  second  vertebra.  The '  trapezius ' 
being  reflected,  the  '  splenius '  is  exposed,  and  beneath  that  the  '  corn- 
plexus/ 

0.  Spines  of  four  cervical  and  six  dorsal  ver- 
tebrae. 


Splenius  capitis  et  colli 


I.    Mastoid  process  and  occipital  bone;  trans- 


verse processes  of  four  upper  cervical  ver- 
tebrae. 

0.  Transverse  processes  of  six  dorsal  and  articu- 
Complexus .                 .  -^          lar  processes  of  four  cervical  vertebras. 

1.  Occipital  bone. 

The  above  muscles  being  reflected,  we  expose  the  muscles  of  the  atlas 
and  axis;  namely,  the  'rectus  capitis  posticus  major'  and  'minor/  'the 
obliquus  superior'  and  'inferior/  and  the  'rectus  capitis  lateralis/ 


0.  Spine  of  the  axis. 

1.  Occipital  bone. 

~  (  0.  Spine  of  the  atlas. 

Kectus  capitis  posticus  minor  .  ^  T 

(  I.  Occipital  bone. 


(  0.  c 
Rectus  capitis  posticus  manor   .  \ 

I  I.    Occipital  bone. 


PLATE  XLV. 


Occipital   "bone 


Interspi-nales 


Superior  articT  facet 
^  dorsal  verteira 


Superior  tubercle. 
/'      (Metapophyais.) 


Inferior  iuberole 
( Anap  opby  s  i 


•RuclimentT  i  ran  sv ' 
process. 


-  -Metapopkysie . 
..  Anapophysie . 


Pig.2 


PLATE  XLVJ. 


PLATE  XLV1I. 


MUSCLES    IN    FRONT    OF    THE    SPINE.  201 

(  0.  Transverse  process  of  atlas. 
Rectus  capitis  lateralis    .        .•<__..  . 

(  I.    Jugular  eminence  of  occipital  bone. 

(  0.  Transverse  process  of  atlas. 
Obliquus  superior   .        .        .  |L    Ocdpital  feone 

(  0.  Spine  of  the  axis. 
Obliquus  inferior    ...-<-.„.  ,    ,_ 

(  I.    Transverse  process  of  atlas. 


MUSCLES  IN  FKONT  OF  THE  SPINE. 
(PLATES  XL VI.  and  XL VII.) 

There  are  three  pre-vertebral  muscles  in  the  cervical  region;  namely, 
the  'rectus  capitis  anticus  major '  and  '  minor/  and  the  'longus  colli.' 
In  the  lumbar  region  are  the  right  and  left  crura  of  the  '  diaphragm/  the 
*psoas  magnus/  and  occasionally  a  'psoas  parvus.' 

0.  Transverse  processes  of  third,  fourth, 
Eectus  capitis  anticus  major  .   -j          fifth,  and  sixth  cervical  vertebrae. 

1.  Basilar  process. 


(  {j 

Eectus  capitis  anticus  minor   .  •< 


0.  Transverse  process  of  atlas. 


Basilar  process. 


The  '  longus  colli '  consists  of  a  longitudinal  and  an  oblique  portion. 
The  longitudinal  part  arises  from  the  bodies  of  the  three  upper  dorsal 
and  two  lower  cervical  vertebras,  and  is  inserted  into  the  bodies  of  the 
second,  third,  and  fourth  cervical  vertebrae.  The  oblique  part  arises  from 
the  transverse  processes  of  the  third,  fourth,  and  fifth  cervical  vertebrae, 
and  is  inserted  into  the  tubercle  of  the  atlas.  Other  oblique  fibres  arise 
from  the  bodies  of  the  three  upper  dorsal  vertebrae,  and  are  inserted  into 
the  transverse  process  of  the  fifth  cervical  vertebra. 

0.  Eight  crus  from  four  lumbar  verte- 
Diaphragm     .        .        .        .  •{          brae,  left  from  three. 

1.  Central  tendon. 

0.  Bodies  and  transverse  processes  of 
Psoas  magnus                           .  -j          all  the  lumbar  vertebrae. 

1.  Trochanter  minor. 

(  0.  Body  of  last  dorsal  vertebra. 
Psoas  parvus  .        .        .        .  •< 

(  I.    Brim  of  pelvis. 


BONES  OF  THE  UPPER  EXTREMITY. 

Component  Bones. — The  bones  of  the  upper  extremity  consist  of 
the  '  clavicle/ the  '  scapula/  the  '  humerus/  the  two  bones  of  the  fore-arm, 
namely,  the  '  radius '  and  the  '  ulna/  the  bones  of  the  carpus,  the  meta- 
carpus, and  the  phalanges  of  the  fingers.  The  clavicles  and  scapulae  form 
the  'shoulder  girdle5  or  'pectoral  arch/  The  length  of  the  arm  should 
be  in  exact  proportion  to  the  height  of  the  individual.  If  the  arms  are 
fully  stretched  in  the  same  horizontal  line,  the  space  from  the  end  of  the 
middle  finger  of  one  hand  to  that  of  the  other  is  about  equal  to  the  length 
of  the  body. 


THE  CLAVICLE. 

(PLATES  XL VIII.,  XLIX.) 

Position  and  Use. — The  clavicle,  or  collar  bone,  so  named  from  its 
resemblance  to  an  ancient  key,  extends  nearly  horizontally  from  the  upper 
part  of  the  sternum  to  the  scapula.  It  keeps  the  shoulders  wide  apart, 
giving  the  arm  a  freer  range  of  motion;  affords  attachment  to  powerful 
muscles;  and  protects  the  axillary  vessels  and  nerves.  By  moving  the 
shoulder,  you  find  that  the  clavicle  acts  as  a  prop,  the  fixed  end  of  the 
prop  being  at  the  sternal  joint.  Hence,  in  fractures  of  the  clavicle,  the 
shoulder  generally  falls  a  little  forward.  The  patient  leans  his  head  to- 
ward the  injured  arm  so  as  to  relax  the  muscles,  and  supports  the  elbow 
in  his  hand. 

Advantage  of  its  Curves. — The  shape  of  the  clavicle  is  like  an 
italic  S.  It  has  two  curves,  arranged  so  that,  viewed  from  the  front,  the 
sternal  or  inner  half  is  convex,  and  the  acromial  or  outer  half  concave. 
The  sternal  curve  is  the  larger  of  the  two.  The  great  vessels  and  nerves 
of  the  arm  pass  under  it.  About  the  junction  of  the  two  curves  the  bone 
is  most  frequently  broken.  These  curves  not  only  make  the  bone  stronger 


PLATE  XLV1II. 


Acromvsil  en<3 


Under  surface  of  clavicle 

Sterno-Yiyoicl . 


.Sternal  end 


ArticuW  surface  ftrclavi'cle 
Coraco'id  process  __, 

Nolth, 


Inferior  a nglft. 

Outer  surface  cf  Scapula. 


Aeromicn. 


Glenoid  cavity 
"Neck, 


THE    CLAVICLE.  203 

than  if  it  were  straight,  but  better  able  to  resist  shocks;  since,  by  virtue 
of  its  elasticity,  the  force  is  partially  broken  at  each  of  the  curves  (p.  5). 
The  strength  and  degree  of  curvature  vary  considerably  in  different  bones. 
They  are  usually  greater  in  men  than  in  women,  and  most  marked  in 
those  persons  who  do  much  manual  labor. 

Shaft. — The  shaft  of  the  clavicle  bears  the  impressions  of  the  muscles 
attached  to  it.  On  its  upper  surface,  at  the  sternal  curve,  are  the  origins 
of  the  '  pectoralis  major '  and  '  sterno-cleido-mastoid/  and  on  the  acromial 
curve,  the  origin  of  the  'deltoid'  and  the  insertion  of  the  'trapezius/ 
On  its  under  surface  are — 1,  a  longitudinal  groove  for  the  insertion  of  the 
'  subclavius ';  2,  a  rough  surface  near  the  sternal  end  for  the  attachment 
of  the  '  costo-clavicular '  (or  rhomboid)  ligament;  3,  near  the  acromial 
end,  a  tubercle  and  a  ridge  for  the  attachment  of  the  'conoid'  and 
'  trapezoid '  ligaments  (coraco-clavicular) :  the  ridge  is  about  one  inch 
from  the  scapular  end — here  fractures  of  the  bone  are  likely  to  escape 
notice,  in  consequence  of  the  ligaments  preventing  the  separation  of  the 
fractured  ends;  4,  near  the  middle  is  a  foramen  for  the  nutrient  artery 
of  the  interior. 

Sternal  End. — The  sternal  end  of  the  clavicle  is  thick,  strong  and 
expanded.  It  is  oblong  from  before  backward,  and  articulates,  through 
the  medium  of  an  interarticular  fibro-cartilage,  with  the  sternum.  In  the 
recent  state,  when  crusted  with  cartilage,  the  articular  surface  is  slightly 
convex  from  above  downward,  and  concave  from  before  backward;  and, 
moreover,  its  circumference  projects  on  all  sides  considerably  beyond 
the  articular  surface  of  the  sternum,  to  which  it  is  so  firmly  attached  by 
its  ligaments  that  dislocation  is  very  rare,  notwithstanding  the  small 
size  of  the  articular  surface  of  the  sternum.  A  fracture  of  the  clavicle  is 
ten  times  more  common  than  a  dislocation  of  its  sternal  end.  Part  of 
the  '  sterno-hyoid '  muscle  arises  from  this  extremity  of  the  clavicle  a  little 
internal  and  posterior  to  the  rough  surface  for  the  rhomboid  ligament. 
At  the  point  where  the  clavicle  comes  into  friction  with  the  cartilage  of 
the  first  rib,  there  is  often  a  distinct  impression,  a  sort  of  improvised  artic- 
ulation blending  with  the  articular  surface  for  the  sternum. 

Acromial  End. — The  acromial  end  is  broad  and  flattened,  and  pre- 
sents an  oblong  surface,  which  looks  forward  and  slants  a  little  inward, 
to  articulate  with  the  inner  border  of  the  acromion.  The  plane  of  this 
articulation  is  such  that  it  is  very  difficult  to  keep  the  clavicle  in  its 
proper  place  after  a  dislocation. 


204  HUMAN    OSTEOLOGY. 

Like  all  the  long  bones,  its  structure  is  spongy  at  the  extremities, 
but  very  compact  in  the  middle  of  the  shaft,  where  there  is  a  small 
medullary  cavity.  The  compact  wall  is  much  thicker  on  the  concave 
side  of  each  of  its  curves  than  elsewhere. 

Connections. — The  clavicle  articulates  with  the  acromion  process  of 
the  scapula,  and  with  the  top  of  the  sternum. 

Ossification. — The  clavicle  begins  to  ossify  about  the  sixth  week  of 
foetal  life,  that  is,  sooner  than  any  other  bone  in  the  body.  It  has  only 
one  centre  of  ossification  for  the  shaft.  The  sternal  end  has  an  epiphysis 
which  makes  its  appearance  from  the  eighteenth  to  the  twentieth  year, 
and  subsequently  coalesces  with  the  shaft. 

Right  or  Left  ? — The  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body  if  he  hold  the  smooth  surface 
upward;  the  flat  acromial  end  outward;  and  the  convex  side  of  the  sternal 
end  forward. 

Comparative  Osteology. — All  Primates  have  clavicles  to  which 
they  owe  the  breadth  of  their  shoulders.  In  the  Carnivora  the  clavicles 
do  not  articulate  with  any  bone,  but  are  simply  suspended  in  the  muscles, 
and  are  always  more  or  less  rudimentary  (see  Felis  leo,  No.  4475).  Bears 
seldom  have  clavicles. 

There  is  no  clavicle  in  the  elephant  (No.  2654),  or  Hyrax  capensis 
(No.  3115  C).  The  three  sub-orders  of  Ungulata  have  no  clavicles,  i.e. 
Pachydermata,  Kuminantia,  Solidungula,  as  the  horse  and  ox.  The  same 
is  true  of  all  Cetacea,  Sirenia  and  Crocodilia. 

The  majority  of  birds  have  clavicles  the  strength  of  which  bears  a 
direct  relation  to  the  powers  of  flight.  They  are  early  anchylosed  together 
in  the  middle  line,  and  form  a  single  bone  called  the  furculum  or  merry- 
thought. The  chief  action  of  this  elastic  arch  of  bone  would  appear  to 
be  to  counteract  the  great  pectoral  muscles  which  tend  to  press  the 
humeri  inward  during  the  downward  stroke  of  the  wing.  The  apteryx 
and  some  parrots  have  no  clavicles. 


THE  SCAPULA. 
(PLATES  XL VIII.,  XLIX.) 

Position  and  Use. — The  scapula,  or  shoulder-blade,  is  placed  at 
the  back  of  the  chest.  When  the  arm  hangs  loosely  by  the  side,  the 
scapula  ought  to  extend  from  the  first  rib  to  about  the  lower  edge  of  the 


PLATE  XLIX. 


Upper  surface  oP  clavicle, 


AtrtmaVenci 


Sternal  end 


Acrormcn 


.Articular  surface  for  clavic!^ 
oraEo-ljrach'ialis 
Short  hea4  op  biceps. 

/.ttacnment  bf  coraco-clavicular  ligaments 
n u.,,'.J«..^  4rj\  iV 


is  miner  t*S 


Pectoral 


Lon^  f)=3f|  nF  biceps. 
Clenoid  cavily. 


-tncep 


Inner  surface  oP  Scapula. 


THE    SCAPULA.  205 

seventh,  and  the  lower  angle  should  be  a  little  further  from  the  spine 
than  the  upper.  The  inferior  angle  of  the  scapula  is  a  good  guide  to  the 
seventh  rib.  During  life  this  angle  is  held  down  by  the  upper  border  of 
the  '  latissimus  dorsi/  and  sometimes  gives  origin  to  some  of  its  fibres. 
In  emaciated  persons  the  yielding  of  this  muscle  allows  the  lower  end  of 
the  scapula  to  project  very  perceptibly. 

The  scapula  acts  as  a  movable  fulcrum  in  the  motions  of  the  arm,  and 
gives  extensive  attachment  to  the  muscles  which  effect  the  movement. 
It  is  a  flat  triangular  bone,  and  so  thin  in  places  as  to  be  translucent. 
We  have  to  examine  its  two  surfaces,  its  three  borders  and  angles,  and 
its  outstanding  processes. 

Outer  Surface. — The  '  outer  surf  ace '  of  the  scapula  ('  dorsum  sca- 
pula ')  is  slightly  convex,  and  divided  into  two  unequal  parts  by  a  very 
prominent  ridge  of  bone,  termed  the  'spine/  The  part  above  the  spine 
is  called  the  supra-spinous  fossa,  and  gives  origin  to  the  '  supra-spinatus ' 
muscle;  that  below  the  spine  is  called  the  infra-spinous  fossa,  and  gives 
origin  to  the  '  inf ra-spinatus.'  Near  the  axillary  border  are  distinct  im- 
pressions, indicating  the  origins  of  the  '  teres  major  *  and  '  minor '  muscles. 
It  is  generally  marked  by  the  impressions  of  the  '  arteria  dorsalis  scapula.' 

Spine  and  Acromion. — The  '  spine '  of  the  scapula  commences  at 
the  posterior  border  of  the  bone  by  a  smooth  triangular  surface  over  which 
the  tendon  of  the  trapezius  plays.  From  this  the  spine  can  be  plainly 
felt  in  the  living  subject  as  it  rises  into  a  high  crest,  which  runs  toward 
the  neck  of  the  scapula,  where  it  stands  out  from  the  rest  of  the  bone, 
and  suddenly  altering  its  direction  at  a  right  angle,  projects  forward  so  as 
to  form  a  lofty  arch  overhanging  the  *  glenoid  cavity.'  This  arch  is  termed 
the  'acromion'  (anpos  ch^os).  It  protects  the  shoulder  joint  and  gives 
great  leverage  to  the  powerful '  deltoid '  which  raises  the  arm.  It  is  not  only 
a  defence,  but  prevents  luxation  upward:  without  this  the  head  of  the  hu- 
merus  would  not  remain  a  moment  in  its  socket.  It  is  this  process  which 
gives  breadth  to  the  shoulder.  On  the  inner  border  of  the  acromion  is 
the  surface  which  articulates  with  the  clavicle;  this  surface  slants  from 
above  inward,  so  that  the  clavicle,  once  dislocated,  is  with  difficulty  kept 
in  its  place.  The  end  of  the  acromion  gives  attachment  to  the  coraco- 
acromial  ligament,  which  bridges  over  the  gap  left  in  the  bone  between  it 
and  the  coracoid  process,  and  thus  completes  the  arch  for  the  shoulder. 
Through  this  coraco-acromial  ligament  we  pass  the  point  of  the  knife,  in 
excising  the  head  of  the  humerus,  and  thus  reach  the  shoulder-joint  in  a. 


206  HUMAN    OSTEOLOGY. 

moment.  Reverting  to  the  spine,  we  observe  that  it  has  thick  rough 
borders;  above,  for  the  insertion  of  the  '  trapezius,'  and  below,  for  the 
origin  of  the  '  deltoid.' 

Inner  Surface. — The  'inner  surface'  of  the  scapula  is  concave,  and 
called  the  '  subscapular  fossa.'  It  gives  origin  to  the  '  subscapularis,'  and 
presents  three  or  four  slanting  ridges  for  the  attachment  of  the  tendinous 
septa  by  which  this  muscle  is  intersected.  The  hollows  between  these 
ridges  were  mistaken,  even  by  the  great  anatomist  Vesalius,  for  the  im- 
pressions of  the  ribs.  On  this  surface  also  observe  the  insertion  of  the 
*  serratus  magnus,'  chiefly  into  the  rough  surfaces  on  the  superior  and  in- 
ferior angles,  but  also  into  a  very  narrow  tract  along  the  posterior  border. 

Glenoid  Cavity. — The  '  anterior  angle '  of  the  scapula  is  the  strongest 
part  of  the  bone,  and  here  is  the  '  glenoid  cavity '  for  the  articulation  of 
the  head  of  the  humerus.  This  cavity  is  very  shallow,  of  an  oval  form, 
with  the  larger  end  downward,  and  the  long  diameter  vertical;  it  looks 
directly  outward  and  a  trifle  forward,  giving  the  arm  an  extensive  range 
of  motion.  Its  margins  are  rather  prominent  and  rough,  for  the  attach- 
ment of  a  collar  of  fibro-cartilage,  which  slightly  deepens  the  socket. 
From  the  upper  part  of  the  margin  arises  the  'long  head  of  the  biceps.' 
Just  below  the  cavity  is  the  origin  of  the  '  long  head  of  the  triceps.'  Im- 
mediately behind  the  cavity  is  a  slight  constriction  termed  the  '  neck '  of 
the  scapula.  The  neck  is  most  plainly  seen  behind,  where  it  forms  with 
the  spine  a  deep  groove  (great  scapular  groove),  leading  from  the  supra- 
spinous  to  the  infra-spinous  fossa. 

When  we  speak  of  fracture  of  the  neck  of  the  scapula,  we  mean  frac- 
ture behind  the  coracoid  process.  This  kind  of  fracture  is  very  rare.  It 
happens  to  old  persons  from  falling  on  the  shoulder.  The  shock  is  re- 
ceived by  the  head  of  the  humerus,  and  is  thence  transmitted  to  the 
glenoid  cavity.  The  chief  symptom  of  such  an  accident  is  slight  lengthen- 
ing of  the  arm  and  dropping  of  the  shoulder.  Whoever  sees  for  the  first 
time  a  fracture  of  the  neck  of  the  scapula  will  probably  mistake  it  for  a 
dislocation  of  the  head  of  the  humerus  into  the  axilla.  There  is  in  each 
case  the  same  lengthening  of  the  arm,  prominence  of  the  acromion,  and 
flatness  of  the  deltoid;  in  each  case  the  head  of  the  humerus  can  be  felt 
in  the  axilla:  but  there  is  this  important  distinction,  that  in  the  case  of 
fracture,  the  normal  appearance  of  the  joint  can  be  restored  by  simply 
pushing  upward  the  arm  at  the  elbow,  by  which  means  the  head  of  the 
humerus,  with  the  gleuoid  cavity,  is  at  once  raised  to  its  proper  position. 


THE    SCAPULA.  207 

Coracoid  Process.— From  the  upper  part  of  the  neck  of  the  scapula, 
just  behind  the  upper  margin  of  the  glenoid  cavity,  stands  off  a  projec- 
tion termed  the  '  coracoid  process,'  from  its  fancied  resemblance  to  the 
beak  of  a  raven  (nopag).  Arising  from  a  very  broad  base,  it  takes  first  a 
direction  inward,  but  soon  curves  forward  toward  the  acromion,  like  a 
half -bent  finger,  and  overhangs  the  glenoid  cavity  on  the  inner  side.  Its 
apex  is  about  one  inch  and  a  half  from  the  point  of  the  acromion,  and 
on  a  lower  plane.  It  is  necessary  to  be  familiar  with  the  direction  of 
these  points  of  bone,  and  their  accurate  bearing  to  the  glenoid  cavity  and 
to  each  other,  since  they  serve  as  landmarks  in  determining  the  nature  of 
obscure  injuries  about  the  shoulder.  Into  the  front  part  of  the  coracoid 
process  is  inserted  the  tendon  of  the  'pectoralis  minor,' and  from  the 
'  apex '  arises  the  common  tendon  of  the  '  coraco-brachialis,'  and  the  '  short 
head  of  the  biceps/  At  the  upper  part  of  its  root  is  a  rough  surface  for 
the  attachment  of  the  '  coraco-clavicular '  ('  conoid '  and  '  trapezoid ')  liga- 
ments which  bind  down  the  clavicle;  and  the  border  next  to  the  acromioii 
gives  attachment  to  the  '  coraco-acromial  ligament,'  which  extends  across 
the  interval  between  these  points  of  bone,  and  completes  the  arch  for  the 
shoulder-joint. 

Three  Borders. — The '  superior  border '  of  the  scapula  presents,  near 
the  root  of  the  coracoid  process,  a  small  notch,  which,  in  the  recent  state, 
is  bridged  over  by  a  ligament.  It  gives  passage  to  the  supra-scapular 
nerve.  Behind  the  notch  is  the  origin  of  the  '  omohyoid '  muscle.  The 
'  posterior  border '  is  always  the  longest  in  man,  and  is  therefore  called 
the  base  of  the  scapula:  in  the  lower  animals  it  is  generally  the  shortest. 
It  gives  insertion  to  the  '  levator  anguli  scapulae,'  the  '  rhomboideus  major ' 
and  '  minor'  muscles,  and,  as  before  mentioned,  to  the  '  serratus  magnus.' 
The  '  inferior  or  axillary  border '  is  by  far  the  thickest  and  strongest,  and 
supports  the  glenoid  cavity.  The  deep  groove  along  it  gives  origin  to 
some  of  the  fibres  of  the  '  sub-scapularis '  muscle. 

Connections. — The  scapula  is  connected  by  its  acromial  process  to 
the  clavicle  which  serves  to  keep  well  apart  the  shoulders.  In  its  glenoid 
cavity  it  receives  the  head  of  the  humerus.  The  '  blade  '  moves  freely  on 
the  ribs,  to  which  it  is  connected  by  muscles  only.  The  sliding  move- 
ment of  the  scapula  on  the  chest  can  be  properly  understood  only  on  the 
living  subject.  It  can  move  not  only  upward  and  downward,  as  in 
shrugging  the  shoulders — backward  and  forward,  as  in  throwing  back  the 
shoulders,  or  in  reaching  forward  as  in  boxing — but  it  has  a  rotatory 


208  HUMAN    OSTEOLOGY. 

movement  round  a  movable  centre.  This  rotation  is  seen  while  the  arm 
is  being  raised  from  the  horizontal  to  the  vertical  position,  and  is  effected 
by  the  co-operation  of  the  trapezius  with  the  serratus  magnus.  The 
glenoid  cavity  is  thus  made  to  look  upward;  the  inferior  angle  slides  for- 
ward, and  is  well  held  under  the  latissimus  dorsi. 

Ossification. — The  scapula  has  seven  centres  of  ossification.  The 
'  primary '  centre,  which  appears  a  little  behind  the  glenoid  cavity  about 
the  seventh  week  of  foetal  life,  forms  all  parts  of  the  bone,  except  the 
coracoid  process,  the  acromion,  the  inferior  angle,  and  the  base:  these 
are  cartilaginous  at  birth.  There  are  two  centres  of  ossification  for  the 
coracoid  process.  The  chief  centre,  representing  the  true  coracoid  bone, 
appears  soon  after  birth,  and  about  the  fifteenth  year  unites  to  the  rest 
of  the  bone.  The  second  centre  is  an  epiphysis  for  the  tip.  About 
puberty,  the  other  secondary  centres  appear;  namely,  two  for  the  acro- 
mion (one  near  the  summit,  the  other  near  the  base);  one  for  the  inferior 
angle;  and,  lastly,  one  for  the  border  of  the  base.  They  all  unite  to 
the  scapula  about  the  twenty-second  year."  In  a  practical  point  of  view 
it  is  well  to  remember  that  the  acromion  is  not  invariably  united  to  the 
spine  by  bone.  In  some  rare  cases  it  remains  permanently  distinct,  and 
is  united  to  the  spine  only  by  ligament,  and  may  be  mistaken  for  a  frac- 
ture. 

Right  or  Left  ? — The  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body,  if  he  hold  the  spine  backward,  the 
acromion  upward,  and  the  glenoid  cavity  outward,  to  receive  the  head  of 
the  humerus  which  is  directed  inward. 

Comparative  Osteology. — The  scapula  is  present  in  all  mammalia. 

In  ruminants  the  coracoid  and  acromion  are  absent. 

The  elephant,  rhinoceros,  pig,  and  tapir  have  a  very  large  process 
at  the  lower  part  of  the  spine,  to  which  in  man  is  attached  a  portion  of 
the  trapezius. 

The  supra-scapular  notch  is  converted  into  a  foramen  by  ossification 
of  the  ligament  in  the  two-toed  sloth  (No.  2387  F). 

The  coracoid  process  is  a  remarkable  bone  in  birds.  In  them  it  is  of 
great  strength  and  solidity,  and  extends  from  the  sternum  to  the  scapula, 

M  The  nucleus  at  the  margin  of  the  glenoid  cavity  is  not  to  be  regarded  as  an 
epiphysis,  but  only  an  occasionally  present  scale,  like  those  sometimes  found  on  the 
coracoid  and  having  no  morphological  bearing,  and  scarcely  worthy  of  notice.  Pro- 
fessor Humphry,  F.R.S. 


Greate 
.lesser 
Btcipital  groove 


a.a, 


Extensor  carpi 


.Extensor  carpi  radiaUs  brevier 

Extensor  fob™  comrnuri 
Extensor  di^iH  minimi 

Extensor  carpi  ulnwo — - 

External  con%le 

Lesser  Head 


Corcno'ii  fossa. 
Internal-  Condyle 
Flexor  carpi  radialis.. 


Trochlea . 
Hum-jn-sranterfor  view. 


.'Flexor  d'l^ilorum  sutiimis 
-Tlexor.  carpi  ulnaris. 


THE     HUMERUS.  209 

where  it  helps  to  form  the  glenoid  cavity.  It  forms  a  buttress  on  each 
side,  which  supports  the  shoulder  during  the  downward  stroke  of  the 
wing.  This  process  never  articulates  with  the  sternum  in  any  mammal 
excepting  in  the  ornithofhynchus  and  the  echidna. 

On  the  top  of  the  sternum  of  the  echidna  (No.  1708)  there  is  a 
T-shaped  bone  called  the  episternum.  On  each  of  its  lateral  branches 
lies  a  thin  plate  of  bone,  which  is  the  clavicle  in  this  animal.  Extending 
forward  from  the  glenoid  cavity  toward  the  top  of  the  sternum  is  a  block 
of  bone  which  corresponds  to  our  coracoid  process,  and  on  the  top  of  this 
is  a  second  piece  of  bone  called  the  epicoracoid.  The  coracoid  being,  as 
we  may  say,  in  two  pieces  is  not  surprising,  seeing  that  in  us  the  cora- 
coid has  two  centres  of  ossification  which  now  and  then  remain  separate. 
This  coracoid  will  be  seen  to  enter  into  the  formation  of  the  glenoid 
cavity. 


THE  HUMERUS. 
(PLATE  L.,  LI.) 

The  humerus  is  the  longest  and  strongest  of  the  bones  of  the  upper 
extremity.  It  is  a  lever  of  the  third  order,  the  fulcrum  being  at  the 
shoulder-joint,  and  the  power  at  the  insertions  of  the  several  muscles 
which  move  the  bone.  It  articulates  with  the  scapula  above,  and  the  ra- 
dius and  ulna  below.  Like  all  the  long  bones  it  has  a  body  or  shaft,  and 
articular  ends. 

Head  and  Neck. — At  the  upper  end  is  the  smooth  eminence  termed 
the  '  head.'  It  forms  about  one-third  of  a  sphere,  and  articulates  with 
the  glenoid  cavity  of  the  scapula.  The  head  of  the  humerus  is  much 
larger  than  the  socket  in  which  it  plays.  This  arrangement,  together  with 
the  shallowness  and  direction  (p.  206)  of  the  socket,  explains  the  great 
range  of  motion  which  the  shoulder-joint  enjoys.  It  is  the  freest  of  all 
the  joints,  and  resembles  what  mechanics  call  a  'universal'  joint:  there 
is  no  part  of  the  body  which  cannot  be  touched  by  one  hand  or  the  other. 
The  head  springs  from  the  shaft  by  a  slightly  constricted  base,  called  the 
'  anatomical  neck,'  to  which  the  capsular  ligament  of  the  joint  is  attached. 
Although  this  is  so  short  and  thick  as  hardly  to  deserve  the  name  of 
neck,  yet  it  serves  the  important  purpose  of  removing  the  head  a  little 

awav  from  the  axis  of  the  shaft.     In  consequence  of  this,  the  axis  of  the 
14 


210  HUMAN    OSTEOLOGY. 

head  and  neck  forms  an  obtuse  angle  with  that  of  the  shaft.  When  the 
arm  hangs  quietly  by  the  side,  with  the  thumb  in  front,  the  precise 
direction  of  the  axis  of  the  head  and  neck  of  the  humerus  is  upward, 
inward,  and  a  little  backward  from  the  shaft — a*  direction  which  facili- 
tates rotation  inward.  In  the  axis  of  the  neck  of  the  femur,  where  rota- 
tion outward  is  more  required  than  rotation  inward,  this  direction  is 
reversed. 

Eaise  the  arm  of  the  skeleton  to  a  right  angle,  and  you  observe  that 
much  of  the  lower  part  of  the  head  of  the  humerus  is  out  of  the  socket. 
This  is  one  of  the  reasons  why  the  humerus  is  so  liable  to  be  dislocated 
when  the  arm  is  extended ;  the  head  of  the  bone  in  this  position  being 
chiefly  supported,  below,  by  the  fibrous  capsule  of  the  joint.  Again, 
when  the  arm  is  raised  to  a  right  angle,  there  is  another  point  worthy  of 
notice:  that  the  humerus  alone  cannot  be  raised  higher,  for  the  reason 
that  the  articular  surface  of  the  head  of  the  bone  does  not  admit  of  eleva- 
tion beyond  a  right  angle.  When  we  do  raise  the  arm  beyond  a  right 
angle,  the  additional  elevation  is  accomplished  by  the  movement  of  the 
scapula  upon  the  chest,  an  effect  chiefly  due  to  the  action  of  the  trapezius 
and  serratus  magnus  muscles. 

Tuberosities. — At  the  root  of  the  neck,  or  rather  at  the  top  of  the 
shaft,  are  two  projections,  termed  the  '  tuberosities/  which  give  greater 
leverage  to  the  muscles  moving  the  bone.  They  are  separated  by  a  per- 
pendicular groove  which  runs  about  three  inches  down  the  shaft,  and  is 
called  the  '  bicipital  groove,'  because  the  tendon  of  the  long  head  of  the 
biceps  plays  in  it.  In  the  recent  state  this  groove  is  bridged  over,  and 
made  into  a  complete  canal,  by  an  aponeurosis.  Of  these  tuberosities 
the  'greater*  is  the  more  external;  in  a  thin  person  it  can  be  plainly  felt 
immediately  below  the  acromion.  It  is  useful  to  know  this  in  determin- 
ing the  nature  of  injuries  about  the  shoulder.  It  has  three  impressions 
indicating  the  insertions  of  muscles,  namely — one  above  and  somewhat  to 
the  front  for  the  '  supra-spinatus,'  a  second  immediately  behind  the  first 
for  the  '  infra-spinatus,'  and  a  third  below  the  second  and  quite  at  the 
back  of  the  bone  for  the  '  teres  minor.'  The  insertion  of  this  last  muscle 
extends  beyond  the  third  impression  nearly  half  an  inch  down  the  shaft. 
The  '  lesser  tuberosity '  is  the  more  internal,  and  gives  insertion  to  the  sub- 
scapularis.  Lastly,  the  tuberosities  are  supported  by  broad  pedicles 
which  run  down  the  shaft,  and  form,  respectively,  the  outer  and  inner 
margins  of  the  bicipital  groove. 


PLATE  LT. 


THE     HOIERUS.  211 

Shaft :  Bicipital  Groove  :  Surgical  Neck.— The  first  thing  to  be 
observed  in  the  shaft  is,  that  its  lower  part  is  twisted  inward,  and  that 
it  is  slightly  curved  forward.  This  twist  and  curve  make  the  axis  of 
motion  at  the  elbow  such,  that  the  fore-arm  naturally  bends  toward  the 
front  of  the  body.  Immediately  below  the  tuberosities  is  the  '  suryiml 
neck '  of  the  humerus;  so  called,  in  contradistinction  to  the  anatomical 
neck  already  described.  Fracture  of  the  surgical  neck  is  common;  of  the 
anatomical  neck  rare.  On  the  front  of  the  shaft  is  the  bicipital  groove, 
up  which  the  long  head  of  the  biceps  runs,  to  be  attached  to  the  top  of 
the  glenoid  cavity,  so  that  it  acts  like  a  strap  and  keeps  down  the  head  of 
the  bone.  Up  this  groove,  too,  a  little  artery  (a  branch  of  the  anterior 
circumflex)  creeps  to  supply  the  joint.  Into  the  outer  margin  of  the 
groove  is  inserted  the  tendon  of  the  '  pectoralis  major ';  into  the  inner 
margin  the  tendon  of  the  '  teres  major ';  and  into  the  bottom  of  it  the 
tendon  of  the  '  latissimus  dorsi.'  These  muscles  play  an  important  part 
in  causing  displacement  in  fracture  when  it  occurs  through  the  surgical 
neck.  There  is  often  a  double  displacement:  i.e.  the  upper  fragment  is 
drawn  outward  by  the  muscles  inserted  into  the  tuberosities,  and  the 
lower  fragment  is  drawn  upward  and  inward  by  the  muscles  which  go 
from  the  trunk  to  the  arm. 

The  middle  of  the  shaft  is  marked  by  ridges  and  impressions  denoting 
the  attachment  of  the  muscles.  Along  its  anterior  aspect  runs  a  very 
prominent  elevation  (the  '  anterior  border '  of  some  anatomist),  continu- 
ous with  the  external  border  of  the  bicipital  groove. 

Deltoid  Ridge. — About  the  middle  of  the  outer  aspect  there  is  a 
rough  impression  (deltoid  ridge)  for  the  insertion  of  the  '  deltoid  '  which 
raises  the  arm.  Near  this,  on  the  inner  aspect,  is  a  smooth  surface  for 
the  insertion  of  the  '  coraco-brachialis.'  Against  this  surface  the  brachial 
artery  can  be  effectually  compressed.  The  surface  looks  forward  and 
inward,  and  as  the  artery  runs  along  it,  the  surgeon  must  remember  this 
obliquity  and  apply  compression  in  the  proper  direction — outward  and 
backward — or  the  artery  will  slip  off  the  bone.  Here  also  is  generally 
situated  the  foramen  for  the  nutrient  artery  of  the  marrow,  which  runs 
from  above  downward.  Below  the  deltoid  ridge  the  shaft  begins  to  be 
twisted,  and  becomes  gradually  flattened  and  expanded  for  the  formation 
of  the  articular  end.  It  is  generally  below  the  insertion  of  the  deltoid 
that  ununited  fractures  of  the  humerus  are  met  with,  partly  on  account 
of  the  injury  to  the  nutrient  artery  of  the  medulla,  and  partly  on  account 


212  HUMAN    OSTEOLOGY. 

of  the  action  of  the  deltoid  in  causing  a  displacement  of  the  upper  frag- 
ment over  the  lower. 

Condyloid  Ridges. — The  lower  half  of  the  shaft  presents  two  ridges, 
one  on  each  side,  called  respectively  the  '  internal '  and  '  external  condyloid 
ridges/  because  they  lead  to  the  '  condyles '  or  points  of  bone  which  pro- 
ject on  each  side  of  the  elbow.  The  external  ridge  begins  just  behind 
the  insertion  of  the  deltoid,  and  is  the  more  prominent  of  the  two;  its 
upper  two-thirds  gives  origin  to  the  '  supinator  radii  longus/  and  its  lower 
third  to  the  '  extensor  carpi  radialis  longior/  It  is  called  the  supinator 
ridge,  and  is  generally  best  developed  in  animals  which  possess  great 
power  in  the  fore-legs  and  paws  for  fighting  or  burrowing.  It  is  rather 
feebly  marked  in  man,  considering  the  mobility  and  strength  of  his  fore- 
arm. The  '  supinator  longus'  is  not  so  much  a  supinator,  as  a  powerful 
assistant  to  the  biceps  and  brachialis  anticus  in  flexing  the  elbow.  The 
internal  ridge  serves  for  the  attachment  of  the  '  internal  intermuscular 
septum.'  The  front  surface  of  this  part  of  the  shaft  gives  origin  to  the 
'  brachialis  anticus/  which  begins  by  two  little  tongues,  one  on  each  side 
of  the  insertion  of  the  deltoid. 

The  back  part  of  the  shaft  is  occupied  by  the  origins  of  the  outer  and 
inner  '  heads  of  the  triceps/  which  are  separated  by  a  groove  directed  in 
a  spiral  manner  downward  and  outward  for  the  passage  of  the  muscnlo- 
spiral  nerve  and  superior  profunda  artery.  The  origin  of  the  outer  head 
is  narrow,  and  lies  external  to  and  above  the  groove,  extending  as  high 
as  the  insertion  of  the  teres  minor.  The  origin  of  the  inner  head  is 
below  the  groove,  reaching  as  high  as  the  lower  limit  of  the  teres  major 
and  covering  all  the  lower  part  of  the  shaft,  even  to  the  external  condyle. 

Lower  End. — The  lower  end  of  the  humerus  curves  slightly  forward, 
and  presents  a  pulley-like  surface,  suited  to  the  flexion  and  extension,  as 
well  as  the  rotatory  movement  of  the  fore-arm.  On  the  outer  side,  we 
observe  the  '  lesser  head '  (capitellum),  which  corresponds  with  the  shal- 
low cavity  at  the  end  of  the  radius.  The  chief  point  about  this  head  is, 
that  it  projects  directly  forward,  so  that  when  the  fore-arm  is  bent  there 
is  a  smooth  surface  ready  for  the  rotation  of  the  radius.  On  the  inner 
side  is  the  '  trochlea '  or  pulley  for  the  ulna.  This  admits  of  flexion  and 
extension  only.  The  direction  of  this  pulley  is  oblique;  that  is,  it  slants 
from  behind  forward,  arid  from  without  inward,  so  that  the  fore-arm,  in 
the  act  of  bending,  comes  naturally  in  front  of  the  chest.  Observe  that 
the  inner  border  of  the  trochlea  descends  much  lower  than  the  outer, 


THE     HUMERUS.  213 

thus  protecting  the  ulna  from  dislocation  inward.  Above  the  trochlea 
there  is  a  deep  cavity  in  front  (coronoid  fossa)  which  receives  the  coronoid 
process  of  the  ulna  in  flexion;  and  a  similar  one  behind  (olecranon  fossa) 
receiving  the  '  olecranon/  or  the  point  of  the  elbow,  in  extension  of  the 
fore-arm.  External  to  the  coronoid  fossa,  immediately  above  the  lesser 
head,  is  a  shallow  depression  for  the  head  of  the 
radius  in  extreme  flexion.  Between  the  '  olec- 
ranon and  coronoid  fossae'  the  bone  is  trans- 
lucent, as  is  well  seen  in  Fig.  59,  which  ex- 
hibits a  section  through  the  joint.  In  con- 
sequence of  this  thinness,  a  transverse  fracture 

FIG.  59.— Section  to  show  the 

through  the  hurnerus  in  this  situation  is  not   Trochlea  rf^eHumerus. 
uncommon.     From  the  displacement  produced  c'  Coronoid  P1™*88- 

so  close  to  the  elbow  joint  this  accident  is  very  liable  to  be  mistaken  for  a 
dislocation  of  the  radius  and  ulna  backward.  However,  the  bearing  of  the 
condyles  with  respect  to  the  olecranon  enables  us  in  most  cases  to  deter- 
mine the  diagnosis.  If  the  olecranou  be  higher  than  the  condyles,  there 
is  dislocation  of  the  elbow;  if  not  higher,  the  ulna  is  in  its  proper  place. 

Condyles. — The  internal  condyle  projects  more  than  the  external, 
and  gives  origin  to  the  powerful  pronator  and  flexors  of  the  hand  and 
fingers,  namely,  to  the  '  pronator  radii  teres/  '  flexor  carpi  radialis,'  '  pal- 
maris  longus/  'flexor  sublimis  digitorum,'  and  'flexor  carpi  ulnaris.' 
The  internal  lateral  ligament  of  the  elbow  is  also  attached  to  it.  The 
external  condyle  gives  origin,  in  front,  to  the  common  tendon  of  the  ex- 
tensor muscles;  namely,  the  '  extensor  carpi  radialis  brevior,'  •'  extensor 
digitorum  communis,'  '  extensor  minimi  digiti,'  and  '  extensor  carpi  ul- 
naris': behind,  it  gives  origin  to  the  'anconeus.'  Lastly,  the  external 
lateral  ligament  of  the  elbow  is  attached  to  it. 

Connections. — The  head  of  the  humerus  articulates  with  the  glenoid 
cavity  of  the  scapula  at  the  shoulder.  At  the  lower  end  on  its  outer  side 
is  a  round  convex  surface  which  articulates  with  the  cup  on  the  top  of 
the  radius;  while  the  trochlea  is  adapted  to  the  form  of  the  sigmoid 
cavity  of  the  ulna. 

Ossification. — The  humerus  has  seven  centres  of  ossification.  There 
is  one  for  the  shaft,  which  appears  about  the  seventh  week  of  foetal  life 
when  the  foetus  is  about  an  inch  long.  About  the  second  year  after  birth 
the  centre  of  the  head  appears;  and  about  the  third  year,  the  centre  of 
the  tuberosities.  About  the  end  of  the  fifth  year,  the  centres  for  the 


214  HUMAN     OSTEOLOGY. 

head  and  tuberosities  have  coalesced,  and  form  a  large  epiphysis  on  the 
top  of  the  shaft.  It  is  necessary  to  remember  that  this  epiphysis  includes 
the  tuberosities  (see  Fig.  60).  On  the  inner  side,  the  line  of  junction 
runs  close  to  the  cartilage  on  the  head  of  the  bone:  there-- 
fore, in  the  event  of  separation,  the  shoulder- joint  would  cer- 
tainly be  implicated. 

About  the  beginning  of  the  third  year,  ossification  of  the 
lower  end  commences  by  a  fourth  centre  in  the  lesser  head. 
About  the  fifth  year,  a  fifth  centre  appears  in  the  internal 
condyle.  About  the  twelfth  year,  a  sixth  centre  appears  in 
the  great  sweep  of  the  trochlea;  and,  lastly,  about  the  four- 
teenth year,  the  seventh  centre  appears  in  the  external 
condyle,  and  uniting  with  the  others  forms  a  large  epiphysis 


Sl£du§estK  at  tlie  lower  end  of  tne  shaft.  The  lower  epiphysis  unites 
to  the  shaft  at  puberty,  while  the  upper  remains  separate 
until  maturity.  Therefore  there  may  be  a  separation  of  the  upper 
epiphysis  from  the  shaft  by  violence  as  late  as  about  the  twenty-first 
year,  but  of  the  lower  end  not  later  than  about  the  sixteenth  year.  (See 
Nor.  Hum.  Ost.,  No.  54.) 

It  is  interesting  to  remark,  that  the  epiphysis  of  the  upper  end,  though 
the  first  to  ossify,  yet  remains  separate  from  the  shaft  about  three  or  four 
years  longer  than  that  of  the  lower  end.  This  is  in  accordance  with  the 
rule,  that,  of  the  epiphyses  of  a  long  bone,  those  toward  which  the  nutri- 
ent artery  of  the  marrow  runs  are  always  the  first  to  unite  with  the  shaft. 
Remember,  that  the  nutrient  arteries  of  the  marrow  of  the  bones  of  the 
upper  extremity  run  toward  the  elbow.  In  the  bones  of  the  lower  ex- 
tremity, they  run  from  the  knee. 

Right  or  Left  ? — The  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body,  if  he  hold  the  rounded  head  up- 
ward and  turned  inward  toward  the  glenoid  cavity,  the  bicipital  groove 
being  in  front. 

Comparative  Osteology.— In  man  the  legs  are  longer  than  the 
arms,  and  grow  faster  than  the  rest  of  the  body  after  birth.  In  apes  and 
monkeys  the  converse  of  this  is  true,  and,  after  birth,  the  arms  grow  faster 
than  the  rest  of  the  body.  In  most  giants  the  great  proportion  of  the 
height  is  due  to  the  length  of  the  lower  extremity.  It  is  curious  that 
the  right  humerus  of  the  gorilla  (No.  5178)  is  of  the  same  length  as  that 
of  the  Irish  giant  O'Brien  (Hum.  Ost.  Ser.,  No.  223),  who  stood  about 


THE     HUMERUS.  215 

eight  feet,  while  the  height  of  the  gorilla  is  only  four  feet  four  inches. 
The  left  humerus  of  O'Brien  is  20  mm.  shorter  than  the  right,  and  there 
exists  a  similar  difference  in  the  two  humeri  of  the  gorilla.  It  may  be 
well  to  mention  that  the  corresponding  bones  of  opposite  sides  commonly 
differ  a  little  in  length,  without  giving  rise  to  any  obvious  deformity. 

The  olecranon  and  coronoid  fossae  occasionally  communicate  by  a  small 
hole  in  man.  This  seems  to  be  pretty  constantly  the  case  in  the  Bush- 
man, gorilla,  tapir  and  dogs.  (See  Separate  Series,  Mus.  Roy.  Coll.  Surg., 
as  well  as  in  the  articulated  skeletons.) 

Above  the  inner  condyle  in  many  carnivora  is  a  foramen  (supra-con- 
dyloid)  which  transmits  the  median  nerve  and  the  brachial  artery.  (See 
Separate  Series,  Mus.  Roy.  Coll.  Surg. :  tiger,  lion,  and  leopard. )  A  trace 
of  this  foramen  occurs  now  and  then  in  man  by  the  ossification  of  a  part 
of  the  fibrous  band  which  passes  over  the  median  nerve  and  from  which 
the  pronator  teres  arises.93 

The  deltoid  ridge  is  especially  prominent  in  the  Carnivora  (see  that  of 
the  seal).  It  is  extensive  in  the  rhinoceros,  the  tapir,  and  the  horse, 
which  have  heavy  limbs  to  raise. 

The  tuberosities  are  very  large  in  the  heavy-limbed  rhinoceros  and  the 
heavy-boned  dugong. 

Notice  how  extensive  the  supinator  ridge  is  in  the  aye-aye  and  the 
beaver. 

In  moles  the  clavicle  articulates  with  the  humerus  (No.  2400  C). 

There  is  no  complete  articulation  between  the  humerus  and  fore-arm 
in  Cetacea,  nor  between  their  carpus,  fore-arm  or  digits;  the  upper  extrem- 
ity forming  a  flipper  which  has  free  movement  only  at  the  shoulder  joint. 
(See  the  Cachalot  Whale.) 

In  flying  birds,  notice  the  large  foramen,  at  which  the  air  enters  the 
cavity  in  the  bone  immediately  below  the  head,  and  feel  the  great  light- 
ness of  their  bones.  The  humerus  of  the  adjutant  (No.  1306)  is  a 
mere  shell.  A  bone  of  this  bird,  thirteen  inches  long,  weighed  only  half 
an  ounce,  while  a  corresponding  one  seventeen  inches  long  of  an  ostrich, 
weighed  half  a  pound,  that  is,  it  was  sixteen  times  as  heavy. 

In  snakes  there  is  no  trace  of  fore-limb,  and  consequently  no  humerus 
(No.  629). 

93  On  the  supra-condyloid  foramen  read  Hyrtl,  "Topogr.  Anat.'  vol.  ii.  p.  283; 
also  Gruber,  '  Canalis  supra  Condyloideus  bumeri,'  Mem/  de  1'Acad.  Imp.  de  St. 
Petersbourg,  1859,  p.  57;  and  Professor  Struthers,  '  Edin.  Med.  Jour.'  1848. 


216  HUMAN    OSTEOLOGY. 

Near  the  end  of  the  humerus  of  the  turtle  there  is  a  line  which  may 
appear  to  denote  an  epiphysis,  but  it  simply  marks  the  limit  to  which 
the  cartilaginous  cap  extended  in  the  recent  bone  (see  No.  1016).  These 
animals  have  no  epiphyses. 


THE    EADIUS. 
(PLATES  LIL,  LIU) 

The  radius  is  the  external  of  the  two  bones  of  the  fore-arm,  and  is  so 
called  from  its  resemblance  to  the  spoke  of  a  wheel.  In  learning  this 
bone,  keep  in  mind  that  both  its  ends  rotate  upon  the  ulna,  and  admit  of 
the  pronation  and  supination  of  the  hand. 

Axis  of  Rotation.  —  In  a  well-articulated  skeleton  the  axis  of  rota- 
tion of  the  radius  is  represented  by  an  imaginary  line  drawn  from  the 
centre  of  the  head  of  the  radius  to  the  centre  of  the  circle  of  which  the 
sigmoid  cavity  at  the  lower  end  is  a  segment;  in  other  words,  to  the 
centre  of  the  lower  end  of  the  ulna.  The  lower  end  of  the  radius  is  much 
larger  than  the  upper,  and  is  the  chief  support  of  the 
hand:  now  since  the  radius  receives  all  shocks  from 
the  hand,  it  is  more  liable  to  be  broken  than  the  ulna. 

Like  the  humerus,  the  radius  and  ulna  are  both 
levers  of  the  third  order,  as  seen  in  Fig.  61.  The 
fulcrum  F  is  at  the  elbow-joint  —  the  weight  to  be 


ff  tto  raised  is  the  fore-arm  W—  the  power  P  is  the  insertion 
of  the  biceps.      The  biceps  acts  to  the  greatest  advan- 
tage when  the  arm  is  bent  to  a  right  angle,  because  the  power  acts  at  a 
right  angle  to  the  lever. 

Head,  Neck,  and  Tubercle.  —  The  upper  end  of  the  radius  is  called 
the  '  head  ':  it  has  a  shallow  circular  cup,  which  articulates  (when  the  fore- 
arm is  bent)  with  the  lesser  head  of  the  humerus,  and  in  the  recent  state 
is  held  in  its  place  by  the  strong  '  orbicular  '  ligament  which  encircles  it. 
Observe  that  the  head  has  a  smooth  circular  border,  which  rotates  in  the 
lesser  sigmoid  cavity  of  the  ulna.  This  rotation  of  the  radius  can  be  dis- 
tinctly felt  in  one's  own  person  below  the  external  condyle  of  the 
humerus;  a  fact  of  great  value  in  determining  the  existence  of  frac- 
ture or  dislocation.  Below  the  head,  is  the  constricted  part  termed  the 
'  neck  ';  and  below  this,  is  the  '  tubercle  '  which  gives  insertion  to  the 


PLATE  LI  I. 


Oler.ra.non 


Greater  s'i|rnoidoavi-ty 
id  cavity 


Coronnicl  -j>n>ceaa. 

2.^ origin  of  Flscor 
SMblimisdi^itoruTn. 
2".a  >>ea4  of  Pronabor  terca. 


Head 

3tyloid  process. 


£tyloid  process 


Radius  Uln» 

Anterior  view. 


THE    EADIU8.  217 

tendon  of  the  '  biceps.'  This  tubercle  projects  on  the  inner  side  of  the 
bone,  so  that  the  biceps  can  supinate,  as  well  as  betid,  the  fore-arm.  The 
posterior  half  of  the  tubercle  is  rough  for  the  insertion  of  the  tendon; 
the  anterior  half  is  smooth,  and  is  the  seat  of  a  bursa  which  facilitates 
the  play  of  the  tendon. 

Shaft. — The  outer  side  of  the  shaft  is  thick  and  rounded;  and  from 
this  side  its  front  and  back  surfaces  gradually  converge  to  a  sharp  edge, 
which  faces  the  ulna  (see  Fig.  62),  and  gives 
attachment  to  the  interosseous  membrane 
represented  by  the  dotted  line.  The  shaft 
is  slightly  arched  outward,  by  which  arrange- 

FIG    62 

ment  it  increases  the  breadth  of  the  forearm, 

and  gives  more  power  to  the  'pronator  teres/84  The  bones  are  fur- 
thest apart  when  the  hand  is  placed  vertically  with  the  thumb  upward: 
hence,  fractures  of  the  fore-arm  are  put  up  with  the  hand  vertical,  that 
there  may  be  less  risk  of  the  opposite  bones  uniting. 

On  the  front  surface  of  the  shaft  there  is  a  blunt  ridge  leading  from  the 
tubercle  obliquely  toward  the  outer  side  of  the  bone.  It  gives  origin  to 
part  of  the  '  flexor  sublimis  digitorum.'  Above  this  ridge  is  the  insertion 
of  the  '  supinator  brevis,'  and  below  it  is  a  slightly  excavated  surface  for 
the  origin  of  the  '  flexor  longus  pollicis.'  Below  this  is  the  insertion  of 
the  '  pronator  quadratus.'  On  the  outer  and  'back  part  of  the  middle  of 
the  shaft  is  a  rough  surface  for  the  insertion  of  the  '  pronator  teres.'  This 
insertion  being  at  the  outer  and  back  part  of  the  shaft,  gives  the  muscle 
greater  power  of  pronation.  In  amputation  of  the  fore-arm  it  is  desira- 
ble to  saw  through  the  bones  below  the  insertion  of  this  muscle,  that  the 
stump  may  have  the  benefit  of  a  pronator. 

The  posterior  surface  of  the  shaft  is  marked  by  the  origin  of  the  ex- 
tensor muscles  of  the  thumb;  namely,  the  '  extensor  ossis  metacarpi  pol- 
licis,' and  the  '  extensor  primi  internodii  pollicis.' 

Lower  End. — The  lower  end  of  the  radius  expands  into  a  surface 
slightly  cupped  transversely,  as  well  as  from  before  backward,  which  ar- 
ticulates with  the  '  scaphoid '  and  '  semilunar '  bones  of  the  carpus.  In  the 
recent  state,  if  not  in  the  dry  bone,  this  surface  is  divided  by  a  slight  ridge; 
the  part  for  the  '  scaphoid '  is  triangular, while  that  for  the  '  semilunar '  bone 
is  square.  On  its  inner  side  is  the  concave  articular  surface  ('  semilunar' 

94  The  radius  of  the  skeleton  of  the  gorilla  in  the  Museum  of  the  College  of  Sur- 
geons is  extremely  arched.  The  power  of  his  arms  is  enormous. 


218  HUMAN    OSTEOLOGY. 

or  '  sigmoid '  cavity),  which  rotates  upon  the  lower  end  of  the  ulna.  On  its 
outer  side  is  the  conical  projection,  termed  the  '  styloid '  process,  of  which 
the  apex  gives  attachment  to  the  external  lateral  ligament  of  the  wrist; 
while  the  base  gives  insertion  to  the  tendon  of  the  '  supinator  radii  lon- 
gus.'  In  front,  the  lower  end  has  a  rough  and  elevated  margin  for  the 
attachment  of  the  powerful  anterior  ligament  of  the  carpus:  and  behind 
there  are  four  grooves  for  the  passage  of  the  extensors  of  the  wrist  and 
fingers.  (Plate  LVI.)  Beginning  from  the  outer  side,  we  observe:  1,  a 
groove  for  the  '  extensor  ossis  metacarpi  pollicis/  and  the  '  extensor  primi 
internodii  pollicis ';  2,  a  groove  for  the  *  extensores  carpi  radiales,  longior ' 
and  '  brevior ';  3,  a  very  distinct  and  slanting  groove  for  the  '  extensor 
secundi  internodii  pollicis ';  4,  a  groove  for  the  '  extensor  indicis '  and  the 
'extensor  communis  digitorum.'  In  the  recent  state  these  grooves  are 
made  complete  canals  by  the  '  posterior  annular  ligament.' 

The  lower  end  of  the  radius  is  composed  of  cancellous  tissue  covered 
by  a  thin  layer  of  compact  bone,  as  shown  in  the  adjoining  Fig.  63.  In 
falls,  therefore,  upon  the  palm  of  the  hand,  the  lower  end 
of  this  bone,  which  receives  the  full  force  of  the  .shock, 
is  very  liable  to  be  broken  transversely  about  half  an  inch 
or  an  inch  above  the  wrist  joint.  This  fracture  of  the 
radius  is  commonly  called  Colles's  fracture,  after  the  Irish 
surgeon  who  first  accurately  described  it.  The  lower 
fragment,  with  the  hand,  is  thrown  backward  so  as  to 
through  the  Lower  make  an  unnatural  swelling  on  the  back  of  the  fore-arm: 

end  of  the  Radius, 

n^oTTteSmp^t  tne  uPPer  fragment  protrudes  on  the  palmar  aspect  of  the 
fore-arm  just  above  the  wrist.  Now  a  fracture  with  such 
displacement  is  liable  to  be  mistaken  for  a  dislocation  of  the  wrist.  The 
two  injuries  may  be  distinguished  as  follows: — If  the  styloid  process  be 
in  the  same  line  with  the  shaft  of  the  radius,  the  injury  is  probably  a  dis- 
location of  the  wrist  backward:  if  it  be  not  in  the  same  line,  there  is 
probably  a,  fracture  of  the  lower  end  of  the  radius,  which  is  by  far  the 
more  frequent  accident  of  the  two. 

Connections. — The  radius  articulates  above  with  the  humerus,  and 
rotates  in  the  lesser  sigmoid  cavity  of  the  ulna.  Below,  it  articulates 
with  the  scaphoid  and  semilunar  bones  of  the  wrist,  and  rotates  upon  the 
head  of  the  ulna. 

Ossification. — The  radius  has  three  centres  of  ossification:  one  for 
the  shaft,  and  one  for  each  end.  The  upper  end  begins  to  ossify  at  the 


PLATE  LIU. 


Olecranon 


Subcutaneous  ncl^e  -from 
•WhicK  arises  aponeurosis  common 
io  the  Plexor  carpt  ulnaris, 
Plexor  dig'r)1pro'!un^ljs' 
Extensor  carpi  ulnaris 


TJlna  Radius 

"Posterior  View 


THE   ULNA.  219 

fifth  year,  and  is  united  at  the  seventeenth.  The  lower  end  begins  about 
the  second  year,  and  is  not  united  till  the  age  of  eighteen  or  twenty. 
(Nor.  Hum.  Ost.,  No.  54.)  This  is  in  accordance  with  the  general  law, 
that  epiphyses  unite  with  the  shafts  in  the  inverse  order  of  their  ossifi- 
cation. 

Right  or  Left  ? — The  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body,  if  he  hold  the  rounded  head  up- 
ward, the  bicipital  tubercle  inward,  and  the  oblique  line  forward. 

Comparative  Osteology. — In  ruminants  the  ulna  and  radius  are 
immovably  united.  The  ulna  is  at  the  back  of  the  radius,  and  forms  a 
very  prominent  olecranon,  on  the  top  of  which  may  be  seen  an  epiphysis 
in  the  fore-limb  of  the  bison. 

In  the  zebra  (Solidungula)  the  ulna  is  represented  by  an  olecranon 
adhering  to  the  back  of  the  radius,  but  in  the  elephant  the  ulna  is  very 
large  and  the  radius  is  small.  (See  the  Separate  Series,  Mus.  Roy.  Coll. 
Surg.) 

In  bats  and  birds  the  radius  is  enormously  long,  forming  the  principal 
support  of  the  wing  in  the  former  (No.  2616  H). 


THE  ULNA. 

(PLATES  LIL,  LIII.) 

The  ulna,  so  called  because  it  forms  the  elbow  (oaXevrf),  is  the  inner  of 
the  two  bones  of  the  fore-arm. 

Upper  End.  —  Its  upper  end  presents  a  deep  semicircular  cavity, 
with  a  smooth  ridge  at  the  bottom,  which  accurately  fits  on  the  trochlea 
of  the  humerus,  and  forms  a  perfect  hinge-joint 
admitting  of  flexion  and  extension  only.  (See 
Fig.  64.)  This  is  called  the  'greater  sig- 
moid' "  cavity,  in  contradistinction  to  a  smaller 
one,  termed  the  'lesser  sigmoid,'  which  is 
placed  on  its  outer  side,  and  forms  a  socket  for  p^  wlse^n  through  the 
the  rotation  of  the  head  of  the  radius.  In  frontGreater8igmoid  cavity  of  the  uina. 
of  the  greater  sigmpid  cavity  is  a  rough  projection,  termed  the  '  coronoid 
process'  (nopGjyjj,  the  top  of  a  curve),  the  rough  surface  in  front  of 


95  So  called  from  its  fancied  resemblance  to  the  letter  Sigma,  which  the  Greeks 
originally  used  in  the  form  of  the  English  C. 


220  HUMAN    OSTEOLOGY. 

which  gives  insertion  to  the  '  brachialis  anticus '  (a  flexor  of  the  fore- 
arm) and  origin  to  the  second  head  of  the  'pronator  teres/  and  the 
second  head  of  the  'flexor  sublimis  digitorum.""  Besides  this,  it  limits 
the  flexion  of  the  fore-arm.  When  the  fore-arm  is  flexed  on  the  arm 
as  much  as  possible,  the  point  of  the  process  strikes  against  the  fossa 
at  the  lower  part  of  the  humerus,  and  prevents  further  flexion.  In 
dislocation  of  the  ulna  backward  the  coronoid  process  is  very  liable  to 
be  broken:  this  complication  makes  reduction  more  easy,  but  subsequent 
retention  of  the  bones  in  their  proper  place  more  difficult.  Ariolent 
action  of  the  brachialis  anticus  may  break  off  the  coronoid  process:  but 
this  is  very  rare.  An  instance  of  this  happened  to  a  boy  about  eight 
years  old,  in  consequence  of  hanging  with  one  hand  from  the  top  of  a 
high  wall.97  "When  it  is  broken,  the  coronoid  process  unites  by  ligament, 
owing  to  the  separation  of  the  fragments  by  the  brachialis  anticus.  At 
the  base  of  the  coronoid  process,  below  the  insertion  of  the  '  brachialis 
anticus/  is  a  rough  tubercular  elevation  for  the  insertion  of  the  oblique 
ligament,  the  other  extremity  of  which  is  attached  to  the  radius  just 
below  the  tubercle  for  the  biceps. 

Olecranon. — Behind  the  sigmoid  cavity  is  the  'olecranon'  (coXevr;, 
elbow,  and  Jtpavov,  head).  This  serves  many  purposes  and  plays  an  im- 
portant part  in  the  perfection  of  the  hinge  of  the  elbow- joint.  It  gives 
leverage  to  the  'triceps/  which  is  inserted  into  it  and  extends  the  fore- 
arm. It  forms  a  convenient  knob  of  bone  for  the  protection  of  the  joint 
when  we  lean  on  the  elbow,  and  it  limits  the  extension  of  the  fore-arm. 
The  surgical  interest  about  it  is,  that  it  is  sometimes  broken  by  a  fall 
upon  the  elbow;  and  the  fracture  generally  takes  place  just  at  the  slight 
constriction  or  notch  where  the  olecranon  joins  the  shaft:  so  that  the 
joint  is  involved  in  the  mischief.  Fractures  of  the  olecranon,  like  those 
of  the  patella  and  coronoid  process,  unite,  generally,  by  ligament,  because 
it  is  so  difficult  to  keep  the  fragments  in  apposition.  But  if  the  tendi- 
nous expansion  from  the  triceps  be  not  torn,  the  union  may  take  place 
by  bone. 

In  almost  all  injuries  about  the  elbow-joint,  however  swollen  the  parts, 
one  can  always  feel  the  olecranon  and  the  internal  condyle  of  the  humerus. 
In  determining,  therefore,  the  nature  of  obscure  injuries  about  this  joint, 

»6  yery  often  the  coronoid  process  gives  origin  to  a  second  head  of  the  flexor  lon- 
gus  pollicis. 

*'  Mr.  Liston,  '  Practical  Surgery.' 


THE   ULNA.  221 

it  is  useful  to  know  that,  when  the  arm  is  extended,  the  tip  of  the  olecra- 
non  and  the  internal  condyle  are  about  one  inch  apart  and  in  the  same 
transverse  line.  When  the  arm  is  bent  to  a  right  angle,  the  olecranon 
is  an  inch  and  a  half  from  the  condyle  and  below  it.  By  this  test  dislo- 
cation of  the  ulna  backward  and  fracture  through  the  lower  end  of  the 
humerus  can  be  distinguished. 

Shaft. — The  shaft  of  the  ulna  is  triangular,  and  tapers  gradually  from 
the  upper  toward  the  lower  end,  which  inclines  a  little  outward  toward 
the  radius  and  terminates  in  the  little  '  head' 
round  which  the  radius  rolls.  A  transverse 
section,  seen  in  Fig.  65,  shows  the  shape  of 
the  radius  and  ulna  about  the  middle.  We 
observe  that  their  sharp  edges  are  turned 

toward  each  other,  and  that  to  these  is  attached  the  interosseous  membrane 
(represented  by  the  dotted  line)  which  connects  the  bones.  Together, 
they  form  a  shallow  concavity  in  front  and  behind,  wherein  the  muscles 
of  the  fore-arm  are  lodged. 

The  greater  part  of  the  front  as  well  as  of  the  inner  surface  of  the 
shaft  is  occupied  by  the  origin  of  the  '  flexor  profundus  digitorum.'  On 
the  front,  too,  is  the  canal  for  the  nutrient  artery  of  the  medulla.  It 
runs  toward  the  elbow  like  that  in  the  radius.  Lower  down  is  the  origin 
of  the  '  pronator  quadratus.'  The  back  part  of  the  shaft  is  marked  by 
ridges  and  surfaces  for  the  muscles  thus: — near  the  elbow  is  the  trian- 
gular surface  for  the  insertion  of  the  '  anconeus ';  next  comes  the  ridge 
for  the  origin  of  the  '  supinator  radii  brevis,'  which  also  arises  from  the 
depression  just  below  the  lesser  sigmoid  cavity.  Below  the  supinator 
brevis  arise  in  succession  parts  of  the  '  extensor  ossis  metacarpi  pollicis/ 
of  the  '  extensor  secundi  internodii  pollicis/  and  also  the  '  indicator.' "" 

Of  the  three  edges  of  the  shaft,  the  external  gives  attachment  to  the 
interosseous  membrane;  the  anterior  is  covered  by  the  origin  of  the 
'  flexor  profundus  digitorum';  the  posterior  gives  attachment  to  a  strong 
aponeurosis,  which  covers  the  muscles  on  the  inner  side  of  the  fore-arm, 
and  affords  additional  surface  for  the  origin  of  the  '  flexor  carpi  ulna- 
ris,'  the  'flexor  profundus  digitorum,'  and  the  '  extensor  carpi  ulnaris.' 
The  posterior  edge  (or  Bridge  of  the  ulna,  as  it  is  generally  called)  de- 
serves the  more  notice,  because  being  subcutaneous  it  can  be  traced  from 

98  It  is  not  uncommon  to  find  that  some  of  the  fibres  of  the  '  extensor  primi  inter- 
nodii pollicis  '  arise  from  the  ulna. 


222  HUMAN    OSTEOLOGY. 

the  olecranon  to  the  styloid  process,  and  is  therefore  an  important  guide 
in  cases  of  doubtful  fracture.  Before  reaching  the  elbow  the  ridge 
bifurcates,  and  encloses  a  triangular  space,  which  is  also  subcutaneous: 
here  we  feel  for  fractures  of  the  olecranon. 

Lower  End. — The  lower  end  of  the  ulna  is  termed  its  '  head/  It  can 
be  plainly  felt  at  the  back  of  the  wrist  when  the  hand  is  pronated.  It  has, 
on  one  side,  a  convex  surface,  forming  rather  more  than  half  a  circle, 
round  which  the  radius,  and  with  it  the  hand,  rotates  to  the  same  extent. 
It  has  also  another  articular  surface,  lined  with  a  synovial  membrane, 
which  looks  toward  the  wrist  joint,  and  corresponds  with  the  interartic- 
ular  fibro-cartilage  interposed  between  it  and  the  cuneiform  bone  of  the 
wrist.  The  ulna  does  not  reach  down  quite  so  low  as  the  radius;  the 
fibre-cartilage,  however,  partly  fills  up  the  interval.  This  difference  in 
the  length  of  the  two  bones  allows  more  extensive  horizontal  movement  of 
the  wrist  toward  the  ulnar  side  of  the  fore-arm. 

The  styloid  process  projects  from  the  lower  end  of  the  lack  part  of 
the  ulna,  and  thus  does  not  interfere  with  the  rotation  of  the  radius;  it 
gives  attachment  to  the  internal  lateral  ligament  of  the  wrist.  Between 
the  process  and  the  head  there  is  a  groove  on  the  posterior  aspect  of  the 
bone  for  the  passage  of  the  tendon  of  the  '  extensor  carpi  ulnaris '  (Plate 
LVL);  and  inferiorly,  the  process  is  separated  from  the  head  by  a  depres- 
sion for  the  attachment  of  the  triangular  fibro-cartilage  of  the  wrist. 

The  styloid  processes  of  the  radius  and  ulna  can  be  readily  felt  beneath 
the  skin,  and  are  important  guides  in  the  determination  of  injuries  of  the 
wrist,  whether  fracture  of  the  radius  or  dislocation.  The  relative  position 
of  the  styloid  processes  with  regard  to  the  axis  of  motion  at  the  wrist 
will  settle  the  question. 

Connections. — The  ulna  articulates,  above,  with  the  trochlea  of 
the  humerus  and  with  the  head  of  the  radius;  below,  it  articulates  with 
the  sigmoid  notch  of  the  radius,  but  is  prevented  from  articulating  with 
the  cuneiform  bone  of  the  wrist,  by  the  intervention  of  an  interarticular 
fibro-cartilage. 

Ossification. — The  ulna  has  three  centres  of  ossification, — one  for 
the  shaft  and  coronoid  process,  one  for  the  lower  end,  and  a  third  for  the 
olecranon.  The  lower  end  begins  to  ossify  about  the  fifth  year,  and  unites 
to  the  shaft  about  the  twentieth.  The  top  of  the  olecranon  remains  car- 
tilaginous until  the  age  of  eight,  about  which  time  it  begins  to  ossify:  it 
coalesces  with  the  base  about  puberty.  (Nor.  Hum.  Ost.,  No.  54.) 


THE    ULNA.  223 

Right  or  Left  ? — The  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body  if  he  hold  the  greater  sigmoid  cavity 
upward;  the  lesser  sigmoid  cavity,  which  receives  the  radius,  outward; 
and  the  styloid  process  behind. 

Comparative  Osteology. — The  ulna  in  many  birds  will  be  seen 
to  be  very  long,  like  the  radius,  forming  the  largest  part  of  the  length 
of  the  wing,  and  to  be  dotted  by  a  line  of  small  tubercles  along  its  outer 
surface  where  the  wing  feathers  are  attached.  See  the  length  of  the 
ulna  in  the  Frigate  bird  (No.  1188  A)  and  the  prominent  feather-tubercles 
in  the  Adjutant  (No.  1306).  Contrast  the  great  length  of  the  ulna  and 
radius  in  the  swift  flying  birds,  as  the  Frigate  (No.  1188  A)  and 
Albatross  (No.  1189)  with  the  shortness  of  those  which  do  not  fly,  as  the 
Great  Auk  (No.  1118),  the  Ostrich  (No.  1362),  and  the  Cassowary  (No. 
1357  A). 


BONES   OF  THE  HAND. 

(PLATES  LIV.,LV.,LVI.) 

THE  skeleton  of  the  hand  consists  of  twenty-seven  bones.  The  first 
eight  are  the  little  bones  of  the  carpus;  the  five  succeeding  bones  con- 
stitute the  metacarpus:  these  support  the  bones  of  the  fingers.  Each 
finger  has  three  bones,  termed,  in  order  from  the  wrist,  the  first,  second, 
and  third  or  ungual  phalanges.  The  thumb  has  only  two  phalanges. 


THE    CARPUS. 
(PLATE  LVI.) 

Number  and  Names. — The  carpus  consists  of  eight  little  bones, 
arranged  in  two  transverse  rows  of  four  bones  each,  thus  forming  a 
broad  base  for  the  support  of  the  hand.  What  is  the  advantage  of  so 
many  bones  in  the  wrist?  It  confers  strength  and  elasticity  and  permits 
some  motion.  The  contiguous  surfaces  are  crusted  with  cartilage  and 
form  synovial  joints.  Suppose  there  had  been  a  single  bone  instead  of  the 
eight  carpal  bones,  how  much  more  liable  it  would  have  been  to  fracture 
and  dislocation.  As  it  is,  dislocation  of  one  or  more  bones  of  the  carpal 
range  is  a  rare  occurrence;  but  it  does  happen  sometimes.  Sir  C.  Bell 
tells  us  that  '  the  boy  that  played  the  dragon  in  a  pantomime  at  Covent 
Garden,  fell  upon  his  hands,  owing  to  the  breaking  of  the  wire  that  sus- 
pended him,  and  he  suffered  dislocation  of  some  of  the  carpal  bones  in  both 
hands.'  The  bones  of  the  carpus  are  named  as  follow,  beginning  from  the 
radial  side: — 

FIRST  OR  PROXIMAL  Row  .  '  SCAPHOID,'  '  SEMILUNAR,'  '  CUNEIFORM,'  '  PISIFORM.  ' 
SECOND  OR  DISTAL  Row    .  '  TRAPEZIUM,  ' '  TRAPEZOID,  ' '  os  MAGNUM,  ' '  UNCIFORM.  ' 

The  student  will  obtain  a  better  idea  of  the  general  shape  and  arrange- 
ment of  these  bones  by  examining  them,  at  first,  collectively.  For  this 
purpose  it  is  very  desirable  that  he  should  have  before  him  an  articulated 
hand,  as  well  as  the  separate  bones. 


PLATE  LIV. 


Plexor  carpi  ulnaris 


Groovef>rFI«xO!-tarpi  rad  ialis 

A-bduclcr  pollicis 

t  poll.cis 


Palmar,  surface-, 


THE    CARPUS.  225 

Carpal  Arch. — The  outline  of  the  carpus  as  a  whole  is  oblong,  with 
the  broad  diameter  in  the  transverse  direction.  Its  bones  are  wedged 
together,  and  so  form  an  arch  with  the  concavity  toward  the  palm,  which 
gives  passage  to  the  flexor  tendons  of  the  fingers.  Fig.  3  in  Plate 
XXXVIII.  snows  that  the  piers  of  the  arch  are  formed  on  one  side  by 
projections  from  the  scaphoid  and  trapezium;  on  the  other,  by  the  pisi- 
form and  the  hook  of  the  unciform.  The  arch  is  converted  into  a  com- 
plete tunnel  by  the  anterior  annular  ligament. 

Radio-carpal  Joint. — To  begin  with  the  bones  of  the  first  row. 
Excluding  the  pisiform,  which  is  only  an  outstanding  '  sesamoid '  bone,  it 
will  be  seen  that  the  scaphoid,  semilunar  and  cuneiform  bones  form  a  con- 
vex articular  surface,  which,  with  the  lower  end  of  the  bones  of  the  fore- 
arm, forms  the  radio-carpal  joint.  This  joint  admits  not  only  of  the  move- 
ments of  flexion  and  extension,  but  also  of  the  horizontal  movements  of 
the  wrist  (abduction  and  adduction).  The  upper  articular  surfaces  of  the 
first  row  of  bones  are  prolonged  further  down  their  dorsal  than  their  pal- 
mar aspect:  hence  the  free  movement  of  extension  at  the  wrist.  The 
articular  surfaces  of  the  scaphoid  and  semilunar  bones  fit  into  the  radius; 
while  that  of  the  cuneiform,  which  is  the  least  extensive  of  the  three, 
would  articulate  with  the  ulna,  but  for  the  intervention  of  the  triangular 
fibro-cartilage  attached,  in  the  recent  state,  to  the  lower  end  of  the  ulna. 
The  bones  of  the  first  row  articulate  with  each  other  by  plane  surfaces 
crusted  with  cartilage,  but  they  are  so  firmly  connected  by  ligaments  that 
there  is  very  little  movement  between  them. 

Intercarpal  Joint. — Collectively,  the  lower  ends  of  the  first  row  form, 
with  the  bones  of  the  second  row,  an  important  movable  joint,  which  we 
call  the  '  intercarpal.'  It  is  very  different  in  form  from  the  first  joint 
(radio-carpal)  of  the  wrist,  since  its  outline  is  alternately  convex  and  con- 
cave. By  means  of  this  second  joint  we  get  a  great  range  of  flexion  and 
extension  at  the  wrist.  If  there  had  been  only  a  single  joint  for  this 
amount  of  motion,  it  would  have  been  comparatively  insecure,  and  very 
liable  to  dislocation,  whereas  dislocation  of  the  wrist  happens  very  rarely 
indeed.  By  reference  to  Plate  LVI.  it  is  seen  that  the  lower  part  of  the 
scaphoid  has  a  convex  articular  surface  which  corresponds  with  the  tra- 
pezium and  trapezoid,  and  also  a  concave  one,  which,  with  a  concavity  in 
the  semilunar  and  cuneiform  bones,  forms  a  deep  socket  for  the  reception 
of  the  head  of  the  os  magnum  and  the  unciform. 

Articulations  of  First  Row. — The  scaphoid  articulates  with  five 
15 


226  HUMAN    OSTEOLOGY. 

bones  inclusive  of  the  radius;  the  semilunar  with  five  inclusive  of  the 
radius;  the  cuneiform  with  three;  and  the  pisiform  with  one,  namely, 
the  cuneiform. 

In  consequence  of  the  flexors  and  extensors  of  the  wrist  being  inserted 
below  the  second  row  of  carpal  bones,  they  necessarily  act  on  the  '  inter- 
carpal  joint '  as  well  as  on  the  radio-carpal.  Thus  a  greater  amount  of 
motion  is  provided  at  the  wrist  than  it  otherwise  could  have  possessed 
with  safety.  If  such  free  motion  had  been  given  to  one  joint,  the  angle 
of  flexion  must  have  been  great  and  the  ligaments  looser  than  would  have 
been  consistent  with  the  security  of  the  joint. 

Bones  of  the  Second  Row. — The  trapezium  and  trapezoid  form 
a  shallow  socket  for  part  of  the  scaphoid,  while  the  os  magnum  and  unci- 
form  form  a  convexity,  which  fits  into  the  deep  socket  formed  by  the  sca- 
phoid, semilunar,  and  cuneiform  in  the  first  row.  Below,  the  second 
row  articulates  with  the  metacarpal  bones,  as  follows:  The  trapezium 
with  two,  that  of  the  thumb  by  a  concavo-convex  surface,  and  partly 
with  that  of  the  index  finger;  the  trapezoid  with  one,  that  of  the  fore- 
finger; the  os  magnum  with  three,  that  of  the  middle  finger,  and  beside 
this  with  those  of  the  index  and  ring  fingers;  and  the  unciform  with 
two,  those  of  the  ring  and  little  fingers.  Thus  the  trapezium  supports  the 
metacarpal  bone  of  the  thumb;  the  trapezoid  that  of  the  index  finger;  the 
os  magnum  that  of  the  middle  finger;  and  the  cuneiform  those  of  the  ring 
and  little  fingers.  The  consequence  is,  that  the  metacarpal  bones  present 
different  degrees  of  mobility, — that  of  the  thumb  being  the  most  movable, 
those  of  the  fore  and  middle  fingers  the  least  so. 

Articulations  of  Second  Row. — Like  the  bones  of  the  first  row, 
those  of  the  second  articulate  with  each  other  by  plane  surfaces  firmly 
connected  by  ligaments.  The  trapezium  articulates  with  four  bones;  the 
trapezoid  with  four;  the  os  magnum  with  seven;  the  unciform  with  five. 

Distinction  of  Individual  Bones. — Thus  far  we  have  examined 
the  bones  of  the  carpus  collectively;  how  are  we  to  distinguish  them  in- 
dividually? Whoever  remembers  what  has  been  already  said,  will  readily 
recognize  the  separate  bones;  and  if  the  rule  laid  down  for  the  parietal 
(page  39),  which  has  been  applied  to  the  other  bones,  be  also  applied  to 
these,  there  cannot  be  much  difficulty  in  determining  to  which  hand  a 
given  bone  belongs. 

Scaphoid  Bone. — The  '  scaphoid '  bone  may  be  told  by  its  boat- 
shaped  socket  (ffnacprf,  a  boat),  by  its  long  narrow  groove  on  the  dorsal  as- 


THE    CARPUS.  227 

pect  between  its  two  convex  surfaces,  and  by  its  '  tubercle '  for  the  attach- 
ment of  the  ligaments  of  the  wrist  (anterior  annular  and  external  lateral). 

Right  or  Left  ? — This  bone  will  be  in  the  same  position  as  the  corre- 
sponding one  in  the  student's  body  if  he  hold  the  concave  surface  forward 
for  articulation  with  the  os  magnum,  the  tubercle  outward  for  articula- 
tion with  the  trapezium  and  trapezoid,  and  the  groove  toward  the  dorsum. 

Semilunar  Bone. — The  '  semilunar '  bone  may  be  told  by  its  semi- 
lunar  shape  (whence  the  name).  There  is  a  narrow  crescentic  surface 
on  its  outer  side  for  articulation  with  a  similar  surface  on  the  scaphoid, 
and  a  broader  crescentic  surface  on  its  inner  side  for  articulation  with  a 
similar  surface  of  the  cuneiform. 

In  the  concavity  of  the  bone  there  are  two  articular  surfaces:  the 
outer,  a  large  one  for  the  head  of  the  os  magnum;  and  the  inner,  a  smaller 
one  for  its  slight  articulation  with  the  unciform. 

Right  or  Left  ? — The  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body  if  he  hold  the  concave  surface  for- 
ward for  articulation  with  the  os  magnum  and  unciform;  the  narrower 
crescentic  surface  outward  for  articulation  with  the  scaphoid,  and  the 
small  non-articular  surface  toward  the  dorsum. 

Cuneiform  Bone. — The  '  cuneiform '  bone  may  be  told  by  its  little 
round  articular  surface  for  the  pisiform  bone,  and  its  concavo-convex 
surface  below  for  the  unciform. 

Right  or  Left  ? — The  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body  if  he  hold  the  crescentic  surface 
outward  for  articulation  with  a  similar  surface  of  the  semilunar;  the  con- 
cave surface  forward  for  articulation  with  a  corresponding  surface  on  the 
*  unciform ';  and  the  round  flat  surface  toward  the  palm  for  articulation 
with  the  pisiform. 

Pisiform  Bone. — The  '  pisiform '  bone  may  be  told  by 
its  pea-shape  (whence  its  name);  and  by  its  round  flat  ar- 
ticular surface  for  the  cuneiform. 

Right  or  Left  ? — This  bone  will  be  in  the  same  posi- 
tion as  the  corresponding  one  in  the  student's  body  if  he 
hold  the  articular  surface  toward  the  dorsum  of  the  hand, 
to  articulate  with  the  cuneiform;  the  projection  forward, 
and  the  groove  toward  the  outer  side.     In  this  position  the  bone  will  be 
seen  to  lean  outward,  toward  the  palm,  thus  resembling  the  unciform 
process  of  the  unciform  bone. 


228  HUMAN    OSTEOLOGY. 

Trapezium. — The  '  trapezium '  (so  named  from  its  shape)  may  be 
told  by  its  saddle-shaped  articular  surface  for  the  metacarpal  bone  of  the 
thumb;  by  the  deep  groove  for  the  tendon  of  the  '  flexor  carpi  radialis/ 
and  the  prominent  ridge  on  the  outer  side  of  that  groove  for  the  attach- 
ment of  the  anterior  annular  ligament,  and  the  origins  of  the  '  opponens 
pollicis '  and  '  abductor  pollicis. 

Right  or  Left  ? — This  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body  if  he  hold  the  tubercle  toward  the 
palm,  the  saddle-shaped  surface  forward  to  articulate  with  the  metacarpal 
bone  of  the  thumb,  and  the  process  which  articulates  with  the  base  of  the 
metacarpal  bone  of  the  index  finger,  inward. 

Trapezoid  Bone. — The  '  trapezoid'  bone  (so  named  from  its  shape) 
may  be  told  by  its  four  articular  surfaces  and  four  angles. 

Right  or  Left  ? — This  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body  if  he  hold  the  small  non-articular 
surface  toward  the  palm;  the  concave  surface  backward  to  articulate  with 
the  scaphoid,  and  the  convex  surface  outward  to  articulate  with  the  tra- 
pezium. 

Os  Magnum. — The  '  os  magnum '  is  the  largest  and  most  important 
of  all  the  carpal  bones.  It  lies  directly  in  the  axis  of  the  hand,  and 
articulates  with  seven  bones.  Its  large  round  '  head '  forms  the  ball  for 
the  socket  in  the  scaphoid  and  semilunar  above.  Its  outer  border  artic- 
ulates with  the  trapezoid;  its  inner  with  the  unciform;  its  lower  with  the 
third  metacarpal  bone  chiefly,  and  also  with  the  second  awd  fourth.  Its 
posterior  dorsal  surface  is  flat  and  roiigh;  its  anterior  bulges  a  little  for- 
ward. 

Right  or  Left  ? — This  bone  will  be  in  the  same  position  as  the 
corresponding  one  in  the  student's  body  if  he  hold  the  convex  head  back- 
ward to  articulate  with  the  concave  surfaces  of  the  scaphoid  and  semilunar; 
the  flattened  articular  surface  inward  for  the  unciform,  and  the  tubercu- 
lated  non-articular  surface  toward  the  palm. 

Unciform  Bone. — The  '  unciform '  bone  may  be  told  by  its  remarka- 
ble hook -like  process;  whence  its  name. 

Right  or  Left  ? — This  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body  if  he  hold  the  convex  surface  back- 
ward for  articulation  with  the  concave  surface  of  the  cuneiform;  the 
unciform  process  toward  the  palmar  aspect,  and  the  flat  surface  for  articu- 
lation with  the  os  magnum  outward. 


PLATE  LV. 


Extensor  carpi  radi 


Extensor  carp>  ulnaris 


Dorsal  surface 


THE   METACARPUS.  229 

Muscles  attached  to  the  Carpal  Bones. — No  muscles  are  con- 
nected with  the  dorsal  surface  of  the  carpus.  On  the  palmar  aspect  the 
pisiform  gives  insertion  to  the  '  flexor  carpi  ulnaris/  and  origin  to  the 
'  abductor  minimi  digiti.'  The  trapezium  gives  origin  by  its  'ridge 'to 
the  '  opponens  pollicis,'  to  parts  of  the  '  abductor  pollicis,'  and  outer  head 
of  the  'flexor  brevis  pollicis.'  The  trapezoid  and  os  magnum  to  the 
'  flexor  brevis  pollicis.'  The  unciform  gives  origin  by  its  '  process'  to  the 
'  flexor  brevis  minimi  digiti,'  and  to  the  '  opponens  minimi  digiti.' 

Ossification. — The  carpus  is  entirely  cartilaginous  at  birth.  Each 
bone  ossifies  from  a  single  nucleus.  The  nucleus  of  the  os  magnum  ap- 
pears in  the  first  year;  that  of  the  unciform  in  the  second;  that  of  the  cunei- 
form in  the  third;  those  of  the  trapezium  and  semilunar  in  the  fifth;  that 
of  the  scaphoid  in  the  eighth;  that  of  the  trapezoid  in  the  ninth;  that  of 
the  pisiform  in  the  twelfth.  This  is  the  last  bone  in  the  body  to  ossify. 

Comparative  Osteology. — In  many  of  the  Carnivora,  as  the  seal, 
walrus,  tiger,  and  dog,  the  scaphoid  and  lunar  are  anchylosed  into  one 
mass.  In  the  bat,  the  scaphoid  lunar  and  cuneiform  form  only  one  bone. 
In  the  dugong,  all  the  carpal  bones  are  anchylosed  into  three  bones,  the 
distal  row  being  in  one  piece. 

In  birds,  as  in  other  animals,  they  are  diminished  in  number  accord- 
ing to  the  disappearance  of  the  digits  which  each  usually  supports. 

The  carpus  of  the  orang-outan,  baboon,  and  several  other  monkeys 
contains  one  more  bone  than  that  of  man,  which  seems  due  to  the  divi- 
sion of  the  scaphoid  into  two  parts.  (See  Separate  Series,  Mus.  Roy.  Coll. 
Surg.) 


THE  METACARPUS. 

(PLATES  LIV.,  LV.) 

The  metacarpus  consists  of  the  five  bones  which  support  the  phalanges 
of  the  thumb  and  fingers.  They  are  described  as  the  first,  second,  third, 
fourth,  and  fifth,  counting  from  that  of  the  thumb;  and,  regarding 
them  as  '  long  bones,'  which  they  much  resemble  in  their  general  struct- 
ure, we  speak  of  their  shafts  and  their  two  ends;  the  upper  end  being 
termed  the  '  base,'  the  lower,  the  '  head '  of  the  bone. 

Shafts. — The  '  shafts '  are  slightly  concave  towards  the  palm,  form- 
ing the  hollow  of  the  hand.  They  are  made  somewhat  triangular  on 
section  by  the  impressions  of  the  '  interosseous '  muscles  which  occupy  tlu- 


230  HUMAN    OSTEOLOGY. 

'  interosseous  spaces/  The  apex  of  the  triangle  is  on  the  palmar  surface, 
the  base  on  the  dorsal  surface  forming  the  support  of  the  extensor  tendons 
of  the  fingers. 

Bases. — Their  '  bases '  articulate  not  only  with  the  bones  of  the  car- 
pus, but,  by  '  lateral  facets,'  with  each  other:  that  of  the  thumb,  how- 
ever, stands  out  alone,  so  as  to  oppose  all  the  others.  It  is  one  of  the 
great  characteristics  of  the  hand  of  man,  that  the  point  of  the  thumb 
can  touch  with  perfect  ease  the  tips  of  all  the  fingers. 

Heads. — The  lower  ends  or  '  heads '  are  rounded  for  articulation  with 
the  first  phalanges  of  the  fingers.  The  articular  surfaces  of  the  heads 
extend  chiefly  toward  the  palm.  They  allow  the  fingers  not  only  to  be 
flexed  and  extended,  but  to  be  moved  laterally.  On  each  side  of  their 
heads  are  a  tubercle  and  a  deep  pit  for  the  attachment  of  the  thick  and 
strong  lateral  ligaments. 

The  shaft  of  each  metacarpal  bone  has  a  canal  for  the  nutrient  artery 
of  the  medulla.  In  the  second,  third,  fourth,  and  fifth  metacarpal  bones, 
the  direction  of  this  canal  is  upward;  but  in  the  metacarpal  bone  of  the 
thumb  its  direction  is  downward. 

Metacarpal  Bone  of  the  Thumb. — The  metacarpal  bone  of  the 

thumb  is  distinguished  by  the  characteristic  saddle-shaped  surface  at  the 

base,  which  articulates  with  the  trapezium.     Besides  which,  its  shaft  is 

l-  shorter,  broader,  and  stronger  than  the  others,  in  accord- 

^Lj^Sjjflfr  ance  w^h  the  many  and  powerful  muscles  which  act  upon 

HOT^^T  **'  There  are  no  less  than  nine  muscles  to  work  the 
Bfl^y  thumb.  Its  great  mobility  in  all  directions,  so  essential 
to  the  power  and  perfection  of  the  human  hand,  depends 
upon  this  saddle-shaped  joint  at  its  base;  and  its  power 
™  '^«  of  antagonizing  the  fingers  is  owing  to  its  base  being  set 

yS^'S^utveS-  off  on  a  Plane  anterior  to  them.  But  for  a  little  buttress 
carpal,  outer  side.  of  kone  which  projects  from  the  inner  and  front  part  of 
the  trapezium,  the  thumb  would  fall  into  the  same  line  as  the  fingers, 
and  would  not  possess  that  power  of  opposing  them  which  makes  the 
human  hand  such  a  wonderful  instrument."  On  the  palmar  aspect  of  its 
head,  observe  two  smooth  surfaces  occasioned  by  the  play  of  the  outer 
and  inner  sesamoid  bones  which  are  connected  with  the  tendons  of  inser- 
tion of  the  '  flexor  brevis  pollicis.' 

Right  or  Left  ? — This  bone  will  be  in  the  same  position  as  the  cor- 
99  Mr.  Lockwood,  Demonstrator  of  Anatomy  at  St.  Bartholomew's  Hospital. 


TJW. 


Radius. 


Extensor  inclicis 


Eybrm'minrn 

.Ex  t?"  carpi  ulnao-'is 


Supinitor  radiilon^us. 
I  Hxtrossts  metacarpi  pollic'is' 
rnnnternoclii  polhws. 


View  of  the  Inter-carpel  Joint, 


THE   METACARPUS.  231 

responding  one  in  the  student's  body  if  he  hold  thfe  rounded  head  forward, 
the  flattened  surface  toward  the  dorsum,  and  the  process  of  bone  at  the 
base  toward  the  inner  side. 

Metacarpal  of  Fore-finger. — The  metacarpal  bone  of  the  fore- 
finger is  distinguished  by  its  deeply  indented  surface  at  the  base,  which 
is  immovably  wedged  with  three  of  the  carpal  bones;  also  by  having  a 
'  lateral  facet '  on  the  inner  side  for  the  third  metacarpal.  (Fig.  68.) 


Inner  side.  Inner  side.  Outer  side. 

FIG.  68.— Base  of  Second  Right  FIGS.  69  and  70.— Base  of  the  Third  Right 

Metacarpal.  Metacarpal. 

Right  or  Left  ? — This  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body  if  he  hold  the  rounded  head  for- 
ward, the  flattened  surface  toward  the  dorsum,  and  the  facet  for  the 
insertion  of  the  extensor  carpi  radialis  longior  outward. 

Metacarpal  of  Middle  Finger. — The  metacarpal  bone  of  the 
middle  finger  may  be  known  by  its  having  a  smooth  square  surface  at  the 
base  for  the  os  magnum,  and  an  angular  projection  at  the  corner  of  it  for 
the  insertion  of  the  '  extensor  carpi  radialis  brevior.'  It  has  also  'lateral 
facets '  on  each  side.  Sometimes,  as  seen  in  Fig.  G9,  the  inner  facet  is 
divided  into  two. 

Right  or  Left  ? — This  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body  if  he  hold  the  rounded  head  for- 
ward, the  flattened  surface  toward  the  dorsum, 
and  the  pointed  process  for  the  insertion  of  the 
extensor  carpi  radialis  brevior  outward. 

Metacarpal  of  Ring  Finger. — The  meta- 
carpal bone  of  the  ring  finger  articulates  with 
the  imciform  and  part  of  the  os  magnum.  It 
may  be  distinguished  by  its  smaller  size:  by  the  inner  side,  outer  side. 

FIGS.  71  and  72.— Base  of  Fourth 

absence  of  the  angular  projection  at  the  base,  Right  Metacarpal. 

which  is  flat;  and  by  its  having  two  facets  on  the  outer  side  and  one 
on  the  inner  (Figs.  71,  72). 


232  HUMAN   OSTEOLOGY. 

Right  or  Left  ? — fThe  bone  will  be  in  the  same  position  as  the  corre- 
sponding one  in  the  student's  body  if  he  hold  the  head  forward,  the  flat- 
tened surface  toward  the  dorsum,  and  the  single  facet  on  the  side  of  the 
base  inward  for  articulation  with  the  metacarpal 
bone  of  the  little  finger. 

Metacarpal  of  Little  Finger.— The  meta- 
carpal bone  of  the  little  finger  may  be  recognized 
by  its  concavo-convex  surface  at  the  base  to  articu- 
late with  the  uncif  orm  bone,  and  by  its  having  only 
one  lateral  facet,  namely,  on  the  outer  side  (Fig. 
Outer  side.  inner  side.  73).  The  projection  on  the  inner  side  of  the  base 

FIGS.  78  and  74.— Base  of      .  .,  .... 

Fifth  Right  MetacarpaL        is  for  the  '  extensor  carpi  ulnaris.' 

Right  or  Left  ? — This  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body  if  he  hold  the  rounded  head  for- 
ward, the  flattened  surface  toward  the  dorsum,  and  the  non-articular  side 
of  the  base  inward. 

Ossification. — Each  metacarpal  bone  has  a  centre  of  ossification  for 
the  shaft  and  proximal  end,  which  appears  about  the  eighth  week  of 
foetal  life.  Each  also  has  an  epiphysis  at  its  distal  end,  of  which  the 
nucleus  appears  about  the  fourth  year.  The  metacarpal  bone  of  the 
thumb,  however,  has  its  epiphysis  at  the  proximal  end,  like  the  pha- 
langes of  the  fingers.  All  unite  to  the  shafts  about  the  twentieth  year.100 
(Nor.  Hum.  Ost.,  No.  54.) 

Comparative  Osteology. — In  all  birds  excepting  the  extinct  archje- 
opteryx  the  metacarpal  bones  are  anchylosed  together.  (See  the  Sepa- 
rate Series  in  the  Mus.  Roy.  Coll.  Surg.) 

Contrast  the  short  metacarpal  bones  of  the  elephant  with  the  enor- 
mously long  ones  of  the  horse  or  giraffe. 

100  To  the  rule  stated  there  are  certainly  exceptions.  I  have  seen  preparations 
clearly  showing  separate  epiphyses  at  the  bases  of  the  metacarpal  bones  of  the 
fore  and  middle  fingers.  I  have  also  seen  a  separate  epiphysis  at  the  head  of  the 
metacarpal  bone  of  the  thumb.  Whether  these  additional  epiphyses  be  normal 
or  exceptional,  they  always  unite  the  first  to  the  shaft,  in  accordance  with  the  direc- 
tion of  the  artery  of  the  marrow,  which  in  the  metacarpal  of  the  thumb  runs  toward 
the  head,  in  those  of  the  fingers  toward  the  base. 


THE  BONES  OF  THE  FINGERS. 

(PLATE  LIV.) 

General  Description. — Each  finger  consists  of  three  bones,  succes- 
sively decreasing  in  size,  and  termed  respectively  the  first,  second,  and 
last  or  ungual  'phalanges.'  The  thumb  has  only  two  phalanges.  A 
general  description  will  suffice  for  all. 

The  structure  of  each  phalanx  is  precisely  like  that  of  the  great  long 
bones,  and  a  longitudinal  section  through  one  of  them  would  display  the 
great  thickness  of  the  compact  wall  of  the  shaft. 

Considering  the  phalanges  as  '  long '  bones,  we  speak  of  their  shafts 
and  their  articular  ends.  The  shafts  are  convex  on  the  dorsal  surface, 
and  flat  on  the  palmar;  on  each  side  of  this  flat  surface  is  a  ridge  for  the 
attachment  of  the  fibrous  sheath  (theca),  which  keeps  the  tendons  in 
their  places. 

First  Phalanges. — The  first  phalanges  are  distinguished  by  their 
greater  length,  and  by  the  shape  of  their  metacarpal  ends,  which  do  not 
form  strictly  hinge- joints,  but  have  concave  oval  surfaces,  with  the  long 
diameters  transverse,  adapted  for  lateral  movement  as  well  as  flexion  on  the 
heads  of  the  metacarpal  bones.  In  accordance  with  this  lateral  move- 
ment, we  observe,  on  each  side,  a  tubercle  for  the  insertion  of  the  in- 
terosseous  muscles  which  produce  it.  Their  distal  ends  are  divided  by 
a  shallow  groove  into  two  little  condyles  with  the  lateral  tubercles  and  de- 
pressions for  the  lateral  ligaments. 

Second  Phalanges. — The  second  phalanges  are  shorter  than  the 
first,  and  are  recognized  by  the  shape  of  their  proximal  ends,  which  have 
two  little  concave  surfaces,  with  an  intervening  ridge,  and  so  form  a  hinge 
with  the  little  condyles  of  the  first  phalanges.  The  first  phalanges  have 
only  one  articular  surface  at  their  proximal  ends,  and  are  thus  distin- 
guished from  the  second.  Each  has  also  a  tubercle  behind,  into  which 
is  inserted  the  extensor  tendon. 

Third  Phalanges. — The  last  or  ungual  phalanges  are  the  shortest. 


234  HUMAN    OSTEOLOGY. 

Their  ends  expand  into  a  horse-shoe  shape,  smooth  on  one  surface  for  the 
support  of  the  nails,  and  rough  on  the  other  for  the  support  of  the  pulp 
of  the  fingers. 

Unequal  Length  of  Fingers. — It  has  been  asked,  What  are  the 
advantages  of  the  fingers  being  of  unequal  length?  Close  them  upon  the 
palm,  and  then  see  whether  or  not  they  correspond.  This  difference  in 
the  length  of  the  fingers  serves  a  thousand  purposes,  to  which  the  works 
of  human  art  and  industry  bear  ample  testimony. 

Ossification.— Each  phalanx  has  two  centres  of  ossification:  one 
for  the  shaft  and  distal  end;  the  other  for  the  proximal  end,  which  remains 
an  epiphysis  till  about  the  twentieth  year.101  (Nor.  Hum.  Ost.,  No.  54.) 

Comparative  Osteology. — In  the  separate  series  in  the  Mus.  Roy. 
Coll.  Surg.  it  will  be  seen  that  the  elephant  has  five  digits;  the  elk  four, 
viz.  the  2nd,  3rd,  4th,  and  5th;  the  ox  two,  the  3rd  and  4th;  the  rhinoceros 
three,  the  2nd,  3rd,  and  4th;  the  tapir  four,  the  2nd,  3rd,  4th,  and  5th; 
the  zebra  and  horse  one,  the  3rd. 

The  flipper  of  the  whale,  which  corresponds  to  the  front  limb,  has  no 
nails:  some  of  the  digits  have  more  than  three  phalanges.  (See  the  round- 
headed  whale,  No.  2518  B,  and  the  lesser  fin- whale.) 

Bats  (Cheiroptera)  have  their  four  ulnar  digits  very  much  elongated, 
forming  the  framework  for  the  wing.  At  least  three  of  these  digits  bear 
no  nails.  The  hook  at  the  top  of  the  bat's  wing  is  the  thumb-nail. 
(See  Sep.  Ser.  Mus.  Eoy.  Coll.  Surg.,  as  well  as  No.  2416  E  and  2416  G 
to  2416  L.) 

In  the  digitigrade  Carnivora,  as  the  tiger  and  cat,  the  sharp  claws  are 
firmly  fixed  into  the  ungual  phalanges,  and  these  are  under  ordinary 
circumstances  bent  backward  on  to  the  back  and  outer  side  of  each  cor- 
responding second  phalanx  by  an  elastic  ligament,  and  are  thus  held  out 
of  the  way  as  long  as  the  flexor  profundus  digitorum  remains  at  rest. 

When  a  cat  pats  you  in  play  she  only  uses  the  flexor  sublimis  digito- 
rum; but  when  she  claws  you  in  anger  she  uses  her  flexor  profundus 
digitorum,  which  flexes  the  ungual  phalanx  and  brings  down  the  claAv. 

That  which  is  commonly  called  the  knee  in  the  horse,  is  really  the 
wrist.  From  this  joint  down  to  the  foot  extends  the  greatly  elongated 
third  metacarpal  bone. 

101  The  centre  of  ossification  in  the  shaft  of  every  long  bone  appears  in  its  middle, 
excepting  in  the  case  of  the  ungual  phalanges,  which  commence  to  ossify  at  their 
distal  ends. 


SESAMOID    BONES. 


235 


In  birds  three  fingers  can  be  traced  as  forming  the  extremity  of 
the  wing.  (See  Sep.  Ser.  Mus.  Roy.  Coll.  Surg.) 

The  phalanges  were  very  numerous  in  the  Ichthyosauria.  (Pal.  Ser., 
No.  222,  Mus.  Eoy.  Coll.  Surg.) 


SESAMOID  BONES. 

(PLATE  LIV.) 

Position  and  Use. — These  little  bones  are  so  called  from  their  re- 
semblance in  size  and  shape  to  the  grain  *  sesamum.'  They  are  met  with 
in  the  substance  of  tendons  in  the  neighborhood  of  joints — the  '  patella,' 
or  'knee-pan/  being  the  best  example.  Their  use  is  to  increase  the 
leverage  of  the  tendons.  The  thumb  has  two  of  these  bones  beneath  its 
metacarpal  joint,  which  increase  the  leverage  of  the  '  flexor  brevis  polli- 
cis.'  We  rarely  find  any  in  the  fingers. 

Comparative  Osteology. — Of  all  animals,  the  mole  has  the  most 
remarkable  apparatus  of  '  sesamoid '  bones.  Its  prodigiously  strong  dig- 
ging feet  are  provided  with  many  of  them,  which  increase  the  leverage  of 
the  brachial  muscles,  and  enable  the  animal  almost  to  swim  through  the 
earth. 

INTEROSSEOUS  MUSCLES. 
Number  and  Arrangement. — There  are  seven  interosseous  muscles 


FIQ.  75.— Four  Dorsal  Interossei,  Drawing 
from  the  Middle  Line. 


FIQ.  76.— Three  Palmar  Interossei.  Drawing 
toward  the  Middle  Line. 


in  the  hand: '"  four  on  the  dorsal  aspect,  and  three  on  the  palmar.     The 

°-  If  we  considered  the  adductor  pollicis  as  a  palmar  interosseous  muscle,  there 
would  be  four  palmar  and  four  dorsal,  all  supplied  by  the  ulnar  nerve. 


236  HUMAN    OSTEOLOGY. 

dorsal  interossei  arise  by  two  heads  from  the  opposed  sides  of  the  meta- 
carpal  bones,  and  are  inserted  into  the  first  phalanges  of  the  fingers,  so 
that  they  separate  the  fingers  from  each  other;  in  other  words,  they  draw 
the  fingers  from  a  stationary  line  supposed  to  pass  down  the  centre  of 
the  middle  finger,  as  represented  by  the  dotted  line  in  Fig.  75. 

The  palmar  interossei  arise  each  from  one  metacarpal  bone,  and  are 
inserted  into  the  fingers,  so  that  they  bring  them  together;  in  fact,  they 
draw  toward  the  stationary  line  down  the  centre  of  the  middle  finger, 
as  shown  in  Fig.  76. 


GENERAL  SURVEY  OF  THE  SKELETON. 

A  GENERAL  survey  of  the  human  skeleton  shows  how  admirably  it  is 
adapted  to  the  erect  attitude. 

Adaptation  of  the  Skeleton  to  the  Erect  Position.— 1.  When 
a  man  stands  erect,  an  imaginary  vertical  plane  (a  b)  supposed  to  fall 
through  the  top  of  the  head,  would  pass  through  the  occipito-atlantoid, 
lumbo-sacral,  sacro-iliac,  hip,  knee,  and    ankle-joints;   in  a 
word,  through  all  the  joints  which  transmit  the  weight  to 
the  ground.      This  explains  why  a  man  can  carry  a  weight  on 
the  top  of  his  head  easier  than  in  any  other  way. 

Position   of  Foramen   Magnum  and  Condyles. — 
2.  The  foramen  magnum  and  the  condyles  of  the  occiput  are 
nearly  horizontal  (when  the  head  is  held  upright)  and  they 
are  advanced  almost  to  the  middle  of  the  base  of  the  skull, 
and  thus  the  head  is  nearly  balanced  on  the  cups  of  the  atlas. 
The  head  has  a  slight  tendency  to  drop  forward,  but  this  is 
limited  by  the  ligamentum  nuchae.     Contrast  the  position  of 
the  condyles  in   the   human  skull  with  that  of  the  orang- 
outan,  in  which  the  condyles  are  not  only  placed  nearer  to 
the  back  of  the  head,  but  obliquely,  making  an  angle  of  40° 
with  the  horizon.     The  lower  we  go  in  the  scale,  the  greater 
is  the  contrast.     In  the  horse,  for  instance,  the  plane  of  the 
condyles  and  foramen  magnum  is  vertical.     In  this,  and  all 
other  herbivorous  quadrupeds,  the  weight  of  the  head  is  sus-      Flo-  77- 
tained  by  an  enormously  strong  and  elastic  ligament  (ligamentum  michse, 
or  pack-wax),  the  strength  of  which  is  in  proportion  to  the  weight  of  the 
head  and  its  tendency  to  drop.     It  extends  from  the  lofty  spines  (withers) 
of  the  anterior  dorsal  vertebrae  to  the  crest  of  the  occiput. 

Direction  of  the  Face. — 3.  The  face  is  placed  perpendicularly 
under  the  cranium,  so  that  the  planes  of  the  face  and  forehead  are  par- 
allel, and  this  characteristic  of  the  human  face  is  well  adapted  for  the 


238  HUMAN    OSTEOLOGY. 

erect  attitude.  If  man  went  011  all  fours,  he  would  habitually  see  and 
smell  nothing  but  the  ground.  As  it  is,  the  direction  of  the  orbits  is  hori- 
zontal, and  therefore  gives  the  greatest  range  of  vision;  and  the  direction 
of  the  nose  gives  the  greatest  range  of  smell.  We  are  reminded  here  of 
the  beautiful  lines — 

'  Pronaque  dum  spectent  animalia  caetera  terram, 
Os  homini  sublime  dedit,  ccelumque  tueri 
Jussit,  et  erectos  ad  sidera  tollere  vultus. ' 

OVID,  Metam.  I.  84-86. 

Breadth  of  the  Thorax. — 4.  The  thorax  is  much  broader  in  the 
transverse  than  in  the  antero-posterior  diameter.  This  great  breadth  of 
the  chest  is  peculiar  to  man  and  the  highest  species  of  ape;  it  throws  the 
arms  farther  apart,  and  gives  them  a  more  extensive  range;  besides  which, 
it  diminishes  the  tendency  there  would  otherwise  be  in  the  trunk  to  fall 
forward.  Contrast  this  with  the  chest  of  quadrupeds,  compressed  later- 
ally and  deep  from  sternum  to  spine,  so  that  the  fore  legs  come  nearer 
together,  and  fall  perpendicularly  under  the  trunk. 

Curves  of  the  Spine. — 5.  The  vertebral  column  gradually  increases 
in  size  toward  the  base.  It  is  curved,  which  makes  it  all  the  stronger, 
and  better  adapted  to  break  and  diffuse  shocks:  and  these  curves,  waving 
alternately,  distribute  the  weight  in  the  line  of  gravity.  This  line  passes 
through  all  the  curves,  and  falls  exactly  on  the  centre  of  the  base.  Ob- 
serve, moreover,  the  length  and  size  of  the  spinous  processes  in  the 
lumbar  region  for  the  origin  of  the  '  erector-spinse.' 

Shape  and  Inclination  of  the  Pelvis.— 6.  The  weight  of  the  ver- 
tebral column  is  supported  on  a  sacrum  broader  in  proportion  than  in 
any  other  animal.  The  iliac  bones  are  widely  expanded  and  concave  in- 
ternally; they  support  the  viscera  and  give  powerful  leverage  to-  the 
muscles  which  balance  the  trunk.  The  whole  pelvis  is  remarkably  broad, 
and  thus  the  base  of  support  is  widened;  and  the  plane  of  its  arch  so 
inclines  as  to  transmit  the  weight  from  the  sacrum  (or  crown  of  the  arch) 
vertically  on  to  the  heads  of  the  thigh  bones:  lastly,  the  deepest  and 
strongest  part  of  the  socket  for  the  thigh  bone  is  in  the  line  of  weight: 
consequently,  the  joint  is  never  more  secure  than  in  the  erect  position. 

With  the  broad  and  capacious  pelvis  of  man,  contrast  the  long  and  nar- 
row pelvis  of  animals,  which,  instead  of  forming  an  angle  with  the  spine, 
is  almost  in  the  same  line  with  it. 


GENERAL    SURVEY    OF    THE    SKELETON.  239 

Lower  Limbs. — 7.  In  proportion  to  the  trunk,  the  lower  limbs  of 
man  are  longer  than  in  any  other  mammal,  the  kangaroo  not  excepted. 
Their  great  length  prevents  their  being  adapted  for  locomotion  in  any  but 
the  erect  attitude.  The  femur  has  a  long  neck,  set  on  to  the  shaft  at  a 
very  open  angle,  so  that  the  base  of  support  is  rendered  still  wider.  The 
long  shaft  of  the  femur  inclines  inward,  bringing  the  weight  well  under 
the  pelvis,  which  is  obviously  of  great  advantage  in  progression:  and 
when  the  leg  is  extended,  the  femur  can  be  brought  into  the  same  line 
with  the  tibia;  thus  the  weight  is  transmitted  vertically  on  to  the  hori- 
zontal plane  of  the  knee-joint,  while  the  articular  surfaces  of  the  bones 
are  expanded  and  give  adequate  extent  of  support. 

Contrast  our  long  lower  limbs  with  the  short  and  bowed  legs  of  the 
gorilla,  chimpanzee,  and  orang-outan.  Watch  attentively  one  of  these 
three  apes  (the  highest  of  the  mammalia  below  man)  in  the  act  of  walking; 
you  will  find  that  he  supports  himself  alternately  on  the  right  and  left 
knuckles  as  well  as  on  his  feet. 

Feet. — 8.  The  foot  of  man  is  broader,  stronger,  and  larger  in  propor- 
tion to  the  size  of  the  body  than  in  any  other  animal;  so  that  man  can 
stand  on  one  leg,  which  no  other  mammal  can  do.  Its  strong  component 
bones  form  a  double  arch  of  exceeding  elasticity,  which  touches  the 
ground  at  both  ends,  and  receives  the  superincumbent  weight  vertically 
on  its  c  crown/  The  great  bulk  and  backward  prolongation  of  the  os 
calcis  at  right  angles  to  the  tibia  support  the  arch  behind,  and  form  a 
powerful  lever  for  the  great  muscles  of  the  calf,  which  raise  the  body  in 
progression,  while  the  bones  of  the  great  toe  are  proportionately  strong, 
and  form  the  chief  support  upon  which  the  body  may  be  raised. 

Upper  Limbs. — 9.  We  see,  then,  that  the  whole  fabric  of  the  skele- 
ton is  so  adjusted  as  to  exempt  the  upper  limbs  from  taking  any  part  in 
its  support.  These  are  kept  wide  apart  by  the  clavicles,  and  their  com- 
ponent joints  admit  of  the  freest  range  of  motion.  The  twenty-seven 
bones  at  the  extremity  of  each  constitute  those  instruments  of  consummate 
perfection,  the  '  HANDS,'  of  which,  even  if  a  formal  dissertation103  had  not 
been  written,  one  might  well  forbear  to  speak,  since  they  have  such  elo- 
quence of  their  own.  '  Nam  caeterae  partes  loquentem  adjuvant,  hae, 
prope  est  ut  dicam,  ipsae  loquuntur:  his  poscimus,  pollicemur,  vocamus, 
dimittimus,  minamur,  supplicamus,  abominamur,  timemus;  gaudium, 

103  <  The  Hand,  its  Mechanism  and  Vital  Endowments,  as  evincing  Design.'  Lon- 
don, 1834,  by  Sir  Charles  Bell,  F.R.S. 


240  HUMAN    OSTEOLOGY. 

tristitiam,  dubitationem,  confessionem,  pcenitentiam,  modum,    copiam, 
numerum,  tempus,  ostendimus.'  104 

Comparative  Osteology. — Some  of  the  vertebrata  have  bones 
which  do  not  exist  in  man  as  such  and  are  only  represented  in  him  by 
fibrous  or  cartilaginous  tissue.  Thus  there  is  the  bone  of  the  heart,  '  os 
cordis,'  in  the  bullock — bos  taurus — (No.  4),  an  example  of  the  visceral 
system  of  bones  or  splanchno-skeleton.  Another  instance  is  the  bony 
sclerotic  of  many  fishes  and  some  birds.  This  is  well  seen  in  a  specimen 
from  the  sun-fish  (No.  5).  There  was  a  ring  of  bone  in  the  sclerotic  of 
the  extinct  flying  lizards  (Pterosauria),  as  well  as  in  that  of  the  Ichthy- 
osauria,  the  life-size  models  of  which  animals  are  seen  at  the  Crystal 
Palace.  In  the  Phocida?,  Trichechus,  the  walras,  and  in  many  dogs,  is 
found  the  '  os  penis'  (Nos.  3906,  3907,  3908,  3909,  and  3910,  the  last 
showing  a  fracture  which  has  been  repaired).  Another  is  the  '  intercla- 
vicula'  found  in  Reptilia.  It  is  often,  too,  present  in  birds,  though  it  is 
in  them  confluent  with  the  clavicles.  In  many  of  the  Lacertilia  a  par- 
tially ossified,  or  cartilaginous  rod  runs  up  from  the  symphysis  of  the 
ischia,  and  supports  the  front  wall  of  the  cloaca,  and  is  called  the  '  os 
cloacae.'  In  all  pouched  animals  (Marsupialia),  as  in  the  kangaroo  (Ma- 
cropus  major,  Ost.  Ser.  Coll.  Surg.  Mus.  1724),  and  in  the  Monotremata 
(that  is,  in  Echidna  and  Ornithorhynchus,  Ost.  Ser.  Coll.  Surg.  Mus. 
1698,  1699),  are  found  the  marsupial  bones:  ossifications,  or  often  only 
chondrifications,  of  the  internal  pillars  of  the  external  abdominal  rings. 

1W  Quintilian. 


PLATE  XXXVIII. 


Qs-TiycMcles, 


.(rreafcer  corn* 
Lesser  cor  nu. 


Body 


.Mylofyoiaeus 


Attachtnentof  ThyroV^1'^ 


ition  for  Thyroid  carVda^e. 


Yer-tical  section  of  oe-'hyoi 


AreK  of  tlie  Carpus. 


CaTc'aneo-scapKo'id  ligamenfc 


OS  HYOIDES. 

(PLATE  xxxvm.) 

Position  and  Use. — The  os  hyoides,  so  called  from  its  likeness 
to  the  Greek  letter  Upsilon,  is  situated  between  the  larynx  and  the  root 
of  the  tongue.  It  is  suspended  from  the  styloid  processes  of  the  tempo- 
ral bones  by  the  stylo-hyoid  ligaments,  often  partly  ossified  in  man,  and, 
generally,  distinct  bones  in  animals.  When  the  neck  is  in  its  natural 
position,  it  can  be  plainly  felt  on  a  level  with  the  lower  jaw,  and  about 
one  inch  and  a  half  behind  it.  It  serves  to  keep  open  the  top  of  the 
larynx,  and  affords  attachment  to  the  muscles  which  move  the  tongue. 

It  is  divided,  for  the  sake  of  description,  into  a  '  body '  or  front  part, 
and  a  '  greater '  and  a  '  lesser  cornu '  on  each  side. 

Body. — The  'body'  (basi-hyal  part)  is  the  thickest  and  strongest 
part.  Its  upper  surface  is  marked  by  the  impressions  of  the  muscles  at- 
tached to  it.  There  are,  generally,  a  transverse  and  a  perpendicular 
ridge:  the  latter  is  in  the  median  line.  Often  there  is  a  little  projection 
from  the  middle,  which  is  interesting  as  a  rudiment  of  the  process  to 
which  is  attached  the  lingual  bone  of  animals  which  runs  into  the  sub- 
stance of  the  tongue.  Its  under  surface  is  slightly  excavated  (as  seen 
in  Plate  XXXVIII.  Fig.  2),  which  shows  a  transverse  section  through 
the  centre  of  the  body.  Into  this  hollow  the  thyroid  cartilage  rises 
behind  the  os  hyoides  in  deglutition.  The  plane  of  the  body  is  nearly 
horizontal;  the  anterior  thyro-hyoid  ligament  is  attached  to  its  posterior 
border. 

Cornua. — The  greater  cornu  (' thyro-hyal '  part)  projects  backward 
about  one  inch  and  a  half,  not  quite  horizontally,  but  with  a  slight  incli- 
nation upward,  and  terminates  in  a  blunt  end,  tipped  with  cartilage. 
Until  the  middle  period  of  life,  the  great  cornu  is  united  to  the  body  by 
cartilage;  but^this  ossifies  in  the  progress  of  age. 

The  lesser  cornu  ('  cerato-hyal '  part)  is  not  much  larger  than  a  barley- 
16 


242  HUMAN    OSTEOLOGY. 

corn,  and  projects  backward  at  an  acute  angle  from  the  junction  of  the 
body  and  the  greater  cornu.  It  articulates  with  the  body  by  a  little 
joint,  and  is  freely  movable:  the  stylo-hyoid  ligament  is  attached  to  the 
end  of  it. 

The  many  muscles  attached  to  the  hyoid  bone  are  shown  in  the  plate. 

The  os  hyoides  is  connected  to  the  thyroid  cartilage  by  three  liga- 
ments, which  contain  a  large  quantity  of  elastic  tissue.  These  ligaments 
are: — 1.  The  anterior  tliyro-hyoid  (Plate  LVII.  Fig.  1),  which  extends 
from  the  '  pomum  Adami '  to  the  upper  and  back  part  of  the  body  of  the 
os  hyoides.  2.  The  two  posterior  thyro-Jiyoid,  which  extend,  one  on 
each  side,  from  the  end  of  the  great  cornu  of  the  os  hyoides  to  the  supe- 
rior cornu  of  the  thyroid  cartilage.  The  vacant  space  left  in  the  dried 
preparation  between  the  hyoid  bone  and  the  thyroid  cartilage  is  closed  in 
the  recent  state  by  the  thyro-hyoid  membrane. 

Ossification. — The  bone  is  ossified  from  five  centres — one  for  the  body, 
and  one  for  each  of  its  four  cornua.  The  body  and  greater  cornua  begin 
to  ossify  in  the  last  month  of  foetal  life.  The  lesser  cornua  begin  to 
ossify  in  the  first  year,  and  generally  in  middle  age  unite  to  the  rest  of 
the  bone. 

Comparative  Osteology. — The  posterior  surface  of  the  hyoid  bone 
is  concave  from  side  to  side  and  from  above  downward.  This  concavity 
is  characteristic  of  the  higher  mammalia.  In  the  gorilla  it  will  lodge 
the  tip  of  the  finger,  while  in  the  howling  monkey,  Mycetes  laniger,  it 
develops  into  a  sac  large  enough  to  hold  a  pigeon's  egg. 

Notice  a  remarkable  anterior  projection  from  the  front  of  the  body 
of  the  hyoid  bone  of  the  horse,  seen  also  more  or  less  in  many  other  ani- 
mals and  especially  in  birds.  (Sep.  Ser.  Mus.  Koy.  Coll.  Surg.) 


PLATE  LVI1. 


THE  LARYNX. 

(PLATE  LVII.) 

Situation  and  Use. — The  larynx  is  situated  at  the  top  of  the 
trachea  or  windpipe.  It  answers  a  double  purpose.  It  guards  the 
opening  through  which  the  air  passes  into  the  lungs:  it  is  the  organ  of 
the  voice  and  of  song.  Its  framework  consists  of  a  number  of  cartilages 
connected  by  joints  and  elastic  ligaments  in  such  a  way  that  they  can  be 
moved  upon  each  other  by  appropriate  muscles;  the  result  of  this  motion 
being  to  act  upon  two  elastic  ligaments  termed  the  '  vocal  cords/  upon 
which  the  voice  essentially  depends. 

Thyroid  Cartilage. — The  thyroid  cartilage  (Ovpeos;  a  shield)  is  so 
named  because  it  shields  the  delicate  apparatus  behind  it.  It  consists  of 
two  lateral  symmetrical  plates  (alas),  united  in  front  at  an  angle  which 
forms  the  prominence  termed  '  pomum  Adami.'  This  prominence,  which 
is  greater  in  the  male  than  in  the  female,  has  a  '  notch '  at  the  upper 
part,  as  if  a  portion  of  the  angle  had  been  sliced  off  to  permit  the  carti- 
lage to  rise  with  greater  facility  behind  the  os  hyoides  in  deglutition. 
More  than  this,  there  is  a  bursa  of  considerable  size  which  diminishes 
friction  between  the  surfaces.  The  bursa  is  practically  interesting,  be- 
cause it  may  enlarge  and  form  a  cyst  in  front  of  the  neck,  sometimes  as 
large  as  a  pigeon's  egg. 

Outer  Surface  and  Ridge. — Look  at  the  outer  surface  of  the  ala 
of  the  thyroid  cartilage  (Fig.  1).  It  has  an  oblique  ridge,  running  down- 
ward and  forward,  with  tubercles  at  each  end,  indicative  of  the  attach- 
ments of  muscles.  The  ridge  gives  origin  to  the  '  thyro-hyoid '  and  inser- 
tion to  the  '  sterno-thyroid '  muscles.  Behind  the  ridge  is  the  origin  of 
the  inferior  constrictor  of  the  pharynx,  extending  down  to  the  side  of  the 
cricoid  cartilage.  The  posterior  border  of  the  ala  is  nearly  vertical,  and 
gives  insertion  to  the  stylo-pharyngeus.  The  inferior  border  of  the  ala 
has  generally  two  curves,  and  gives  insertion  to  the  '  crico-thyroid ' 
muscle.  This  muscle  arises  from  the  side  of  the  cricoid  cartilage;  conse- 
quently, when  it  acts,  it  draws  the  two  cartilages  together. 


244  HUMAN    OSTEOLOGY. 

Cornua. — The  posterior  part  of  each  ala  has  two  projections,  termed 
its  '  cornua '  superior  and  inferior.  The  superior  cornu  gives  attachment 
to  the  posterior  thyro-hyoid  ligament.  The  inferior  cornu  articulates 
with  the  cricoid  cartilage.  This  is  a  perfect  joint,  provided  with  a  syno- 
vial  membrane  and  ligaments.  It  is  important  to  remember  that  the 
form  of  the  joint  admits  of  only  vertical  movement  of  the  thyroid  carti- 
lage, the  axis  of  motion  being  a  transverse  line  drawn  through  both  joints. 
Upon  this  movement  depends  the  tuning  of  the  vocal  cords. 

Angle. — So  much  for  the  outside  of  the  thyroid  cartilage.  Now  for 
the  parts  attached  within  the  angle.  To  see  them  properly,  one  of  the 
ala3  should  be  removed,  as  in  Fig.  2.  You  then  observe  that  the  follow- 
ing objects  are  attached  to  the  angle,  beginning  at  the  top:  1,  the  anterior 
thyro-hyoid  ligament;  2,  below  this,  the  apex  of  the  epiglottis;  3,  lower 
down,  the  false  vocal  cords;  4,  still  lower,  the  true  vocal  cords;  5,  below 
these,  the  origin  of  the  '  thyro-arytenoideus ';  lastly,  at  the  lower  border 
of  the  angle,  is  the  attachment  of  the  '  crico-thyroid '  ligament. 

Cricoid  Cartilage. — The  cricoid  cartilage  (Plate  LVII.)  forms  a 
complete  ring  (whence  its  name),  a  little  broader  in  the  antero-posterior 
diameter  than  in  the  transverse.  It  is  situated  at  the  top  of  the  trachea, 
immediately  below  the  thyroid  cartilage.  The  ring  is  not  of  the  same 
depth  all  round.  It  is  narrow  in  front,  and  from  this  part  the  upper 
border  of  the  ring  gradually  rises,  so  that,  behind,  the  ring  is  a  full  inch 
in  vertical  depth,  and  occupies  part  of  the  interval  between  the  alas  of 
the  thyroid.  This  slope  of  the  cricoid  toward  the  front  permits  the  ver- 
tical play  of  the  thyroid.  It  cannot  be  too  strongly  impressed  upon  a 
student  that  he  should  make  his  finger  familiar,  in  his  own  neck,  with 
the  projections  of  the  thyroid  and  the  cricoid  cartilages,  and  the  slight 
depression  between  them,  indicating  the  site  of  the  crico-thyroid  mem- 
brane. These  parts  lie,  one  below  the  other,  in  the  middle  line  of  the 
neck,  and  are  the  guides  in  the  operation  of  laryngotomy  and  trache- 
otomy. The  operation  of  laryngotomy  consists  in  dividing  the  crico-thy- 
roid ligament  transversely  close  to  the  cricoid  cartilage,  that  the  incision 
may  be  as  distant  as  possible  from  the  vocal  cords. 

Passing  from  the  front  toward  the  side  of  the  cricoid  cartilage,  notice 
the  origin  of  three  muscles,  namely — the  '  crico-arytenoideus  lateralis ' 
along  the  upper  edge  (Fig.  2);  the  '  crico-thyroid '  in  the  middle  (Fig. 
1);  and,  lower  down,  a  portion  of  the  '  inferior  constrictor  of  the  pharynx/ 

At  the  back  part  of  the  cricoid  cartilage  (Fig.  3)  there  is  on  either 


THE    LARYNX.  245 

side  a  broad  excavation  for  the  origin  of  the  t  crico-arytenoideus  posticus. ' 
Generally  these  muscles  are  separated  by  a  slight  vertical  crest  which 
gives  attachment  to  some  of  the  longitudinal  fibres  of  the  oesophagus.  At 
the  top  of  the  cricoid  are  the  two  small  oval  articular  surfaces,  one  on 
each  side,  for  the  arytenoid  cartilages,  to  be  examined  presently. 

The  side  of  the  cricoid  articulates  with  the  inferior  cornu  of  the  thyroid 
cartilage  by  means  of  a  perfect  joint,  provided  with  a  synovial  membrane 
and  ligaments.  The  structure  of  this  joint  permits  the  two  cartilages  so 
to  move  upon  each  other  that  their  opposite  borders  can  be  approximated 
Tsy  the  '  crico-thyroid '  muscle.  It  deserves  especial  attention,  because  the 
degree  of  this  approximation  regulates  the  tension  of  the  vocal  cords. 

Lastly,  the  lower  border  of  the  cricoid  is  horizontal,  and  connected  to 
the  first  ring  of  the  trachea  by  an  elastic  membrane. 

Arytenoid  Cartilages  and  Cornicula  Laryngis. — The  arytenoid 
cartilages,  so  named  from  their  resemblance  to  an  ancient  ewer(apvTcn va), 
are  situated,  one  on  each  side,  at  the  upper  part  of  the  cricoid  (Fig.  3). 
Each  is  somewhat  pyramidal  in  form,  with  the  apex  above,  looking  to- 
ward its  fellow,  and  slightly  curved  backward.  The  apex  of  each  is  sur- 
mounted by  a  nodule  of  cartilage,  termed  the  '  cartilage  of  Santorini ' 
{'corniculum  laryngis').  The  base  presents  an  oval  concave  surface, 
which  forms  a  perfect  joint,  with  a  corresponding  convex  surface,  on  the 
cricoid  cartilage.  This  joint  has  a  loose  synovial  membrane  and  liga- 
ments, so  that  the  arytenoid  cartilages  admit  of  being  approximated  or 
separated,  a  freedom  of  motion  which  is  essential  to  the  dilatation  and 
contraction  of  the  glottis  or  chink  between  the  true  vocal  cords  through 
which  the  air  enters  the  trachea. 

Tubercles  of  the  Arytenoid. — At  the  base  of  each  arytenoid  car- 
tilage (Plate  LVIL  Fig.  2)  observe  the  anterior  tubercle  to  which  the 
true  vocal  cord  is  attached,  and  the  posterior  tubercle,  which  gives  inser- 
tion to  two  muscles — namely,  the  '  crico-arytenoideus  lateralis '  and  the 
*  crico-arytenoideus  posticus ':  these  muscles  are  inserted,  not  into  the 
same  side,  but  into  opposite  sides  of  the  tubercle  :  the  effect  of  which  is 
that  they  antagonize  each  other. 

Each  arytenoid  cartilage  has  three  surfaces — a  posterior,  an  anterior 
or  external,  and  an  internal.  The  posterior  surface  is  excavated  and  has 
attached  to  it  the  *  arytenoideus '  muscle  (Fig.  3),  which  crosses  from  one 
curtilage  to  the  other,  and  fills  up  the  gap  between  them.  The  anterior 
surface  is  also  excavated,  and  occupied  by  the  insertions  of  the  '  crico- 


246  HUMAN   OSTEOLOGY. 

arytenoideus  lateralis '  and  the  '  thyro-arytenoideus.'  The  internal  sur- 
face is  flat,  looks  toward  its  fellow  of  the  opposite  side,  and  contributes 
to  form  part  of  the  margin  of  the  glottis. 

Epiglottis. — The  epiglottis  is  a  structure  composed  of  yellow  elastic 
cartilage  situated  at  the  base  of  the  tongue,  and  projecting  over  the  upper 
part  of  the  larynx  like  the  flap  of  a  valve.  In  shape  it  somewhat  resem- 
bles the  leaf  of  an  artichoke.  Its  apex  is  attached  to  the  angle  of  the 
thyroid  cartilage.  Its  ordinary  position  is  perpendicular,  or  nearly  so, 
leaving  the  glottis  free  for  respiration;  but  during  deglutition  the  larynx 
is  raised,  and  the  tongue  is  depressed,  so  that  the  epiglottis  becomes  more 
horizontal,  drops  like  a  valve  over  the  top  of  the  larynx,  and  tends  to 
prevent  the  entrance  of  food  into  it.  This  falling  of  the  epiglottis  is  not 
produced  by  any  special  muscle;  it  is  simply  mechanical. 

Cuneiform  Cartilages. — These  cartilages  are  the  smallest  and  least 
essential  of  the  whole  group.  They  are  found  in  the  '  aryteno-epiglot- 
tidean  fold/  a  prominent  line  of  mucous  membrane  running  on  each 
side  from  the  edge  of  the  epiglottis  to  the  apex  of  the  arytenoid  cartilage. 
They  are  thin  and  narrow,  not  much  larger  than  pins'  heads  and  not 
constant. 

Thus  there  are  nine  cartilages  in  all,  of  which  four — namely,  the  thy- 
roid, cricoid  and  two  arytenoid — are  composed  of  hyaline  cartilage  and 
are  prone  to  ossify  in  old  age.  The  remaining  five  are  of  yellow  elastic 
fibre-cartilage,  and  have  but  little  tendency  to  ossify. 

Vocal  Cords,  True  and  False. — The  vocal  cords  are  four  elastic 
ligaments,  two  on  each  side,  extending  horizontally  backward  from  the 
angle  of  the  thyroid  cartilage  to  the  anterior  part  of  the  arytenoid.  The 
two  lower,  and  the  most  important,  are  termed  the  '  true '  vocal  cords,  be- 
cause, by  their  vibration,  they  produce  the  voice  :  the  two  upper  cords 
are  called  'false/  because  they  have  little  or  nothing  to  do  with  the 
voice.  The  rapidity  and  accuracy  with  which  the  true  vocal  cords  can 
change  their  tension,  their  form,  and  the  width  of  the  slit  between  them, 
render  the  voice  the  most  perfect  of  musical  instruments. 

Attachments  of  Vocal  Cords. — The  precise  attachments  of  these 
cords  are  best  seen  in  the  dried  larynx,  in  which  all  the  surrounding  soft 
parts  have  been  removed,  as  shown  in  Plate  LVII.  Fig.  2.  The  true 
vocal  cords  are  attached  in  front  close  together  to  the  angle  of  the  thyroid 
cartilage,  about  a  quarter  of  an  inch  from  its  lower  edge,  and  they  diverge 
as  they  pass  backward  to  be  attached  to  the  anterior  tubercle  of  the  base 


THE    LARYNX. 


247 


of  the  arytenoid.  The  false  cords  also  proceed  from  the  angle  of  the 
thyroid  a  little  higher  than  the  true,  to  about  the  middle  of  the  front 
part  of  the  arytenoid.  In  the  recent  larynx  these  cords  are  not  free 
all  round,  like  the  strings  of  a  violin;  they  are  Only  free  along  the  sides 
which  face  each  other;  everywhere  else  the  true  cords  are  in  contact  with 
muscle,  and  the  false  with  fat  and  areolar  tissue. 

Length  of  Vocal  Cords.— What  is  the  length  of  the  true  vocal 
cords?  During  life,  their  length  is  continually  varying,  to  a  slight 
degree,  with  the  pitch  of  the  voice;  but,  in  the  dead  subject,  they  are 
about  five-eighths  of  an  inch  in  the  adult  male.  From  an  examination 
of  several  male  larynges,  the  cords  are  found  to  differ  more  or  less  in 
length  in  different  individuals,  though  not  more  than  one-twelfth  of  an 
inch.  These  individual  differences  in  the  length  of  the  cords  make  cor- 
responding variations  in  the  natural  tone  of  the  voice:  e.g.  tenor,  bary- 
tone, or  base.  A  deep  voice  coincides  with  the  longer  cords;  a  shrill 
voice  with  the  shorter.  In  the  female  the  cords  are  about  one-fourth 
shorter  than  in  the  male.  In  boys,  too,  they  are  much  shorter  than  in  the 
adult;  hence  the  peculiar  voice  of  boys.  At  puberty  the  cords  lengthen 
with  the  development  of  the  larynx,  and  the  voice  is  said  to  break. 


Epiglottis 


Thyroid  cartilage 

False  vocal  cord 
Ventricle 
True  vocal  cord 


Rima  glottidis. 


Thyro-arytenoideus  muscle 

Cricoid  cartilage 
Trachea 


FIG.  78.— Perpendicular  Section,  showing  the  Ventricles  of  the  Larynx. 

Ventricles  of  the  Larynx. — In  the  perfect  larynx  is  a  little  recess 
on  each  side  between  the  true  and  the  false  vocal  cords,  like  a  little  side 
pocket.  These  recesses  are  called  'the  ventricles'  of  the  larynx,  and 


248  HUMAN    OSTEOLOGY. 

are  best  examined  by  cutting  open  the  larynx.  Their  shape,  depth  and 
situation  are  represented  in  the  outline  of  the  subjoined  Fig.  78,  taken 
from  a  transverse  perpendicular  section  of  the  larynx.  They  appear  to 
allow  free  space  for  the  vibration  of  the  vocal  cords  and  probably  strengthen 
the  voice.  They  are  lined  by  the  mucous  membrane  of  the  larynx,  and 
the  bottom  of  each  is  supported  by  the  '  thyro-arytenoideus '  muscle.  The 
length  of  the  ventricles  from  before  backward  corresponds  with  the  length 
of  the  vocal  cords.  Their  greatest  vertical  depth  is  toward  the  front, 
which  is  the  part  represented  in  the  section. 

Size  of  the  Ventricles. — The  ventricles  of  the  larynx  are  large 
enough  to  lodge  a  foreign  body,  such  as  a  pea.  A  pill  forced  down  a 
child's  throat  against  its  will  has  been  known  to  catch  in  one  of  the  ventri- 
cles, and  occasion  death,  after  a  few  struggles,  from  spasm  of  the  glottis. 

Rima  Glottidis. — The  term  '  rima  glottidis '  or  '  glottis '  is  applied  to 
the  interval  between  the  true  vocal  cords  through  which  the  air  passes 
into  and  out  of  the  trachea.  It  is  about  one  inch  in  length.  Its  boun- 

Thyroid  cartilage.       darleS  (FiS'  79)  ar6  f  °1TOed  ^  the  VOCal 

TTU  v  i  cord  cords  and  by  the  arytenoid  cartilages. 
The  vocal  cords  form  about  the  anterior 
two-thirds,  the  cartilages  about  the 
posterior  third  of  the  opening.  The 

Arytenoid  cartilage.    r 

glottis  admits  of  being  made  wider,  or 

Elastic  ligament. 

narrower,  or  may  even  be  completely 
FIG.  79.-shape  of  the  Glottis  when  at  rest.  ciosea,  by  the  action  of  muscles  which 
we  shall  examine  presently.  In  a  state  of  rest  it  is  triangular;  the  apex 
being  in  front  at  the  thyroid  cartilage,  and  the  base  between  the  aryte- 
noid, as  shown  in  Fig.  79,  where  the  arytenoid  are  cut  through  on  a  level 
with  the  vocal  cords.  When  the  glottis  is  dilated  in  inspiration  by  the 
*  crico-arytenoidei  postici,' it  becomes  spear-shaped,  as  seen  in  Fig.  81. 
During  expiration  the  glottis  gradually  resumes  its  triangular  shape  or 
state  of  rest;  and  this  return  to  a  state  of  repose  is  effected,  not  by  muscle, 
but  by  an  elastic  ligament  shown  in  Fig.  81,  which  draws  the  arytenoid 
cartilages  toward  the  mesial  line.  The  glottis,  like  the  chest,  is  dilated 
during  inspiration  by  muscular  tissue;  like  the  chest,  also,  it  is  contracted 
during  expiration  by  elastic  tissue. 

Muscles  of  the  Larynx. — There  are  nine  muscles  which  act  spe- 
cially upon  the  rima  glottidis — four  on  each  side,  and  one  in  the  middle. 
The  four  on  each  side  are  the  '  crico-thyroidei,'  the  '  crico-arytenoidei 


THE    LARYNX. 


249 


postici,'  the  'crico  arytenoidei  laterales,'  and  the   '  thyro-arytenoidei.' 
The  single  one  in  the  middle  is  the  '  arytenoideus. ' 

Crico-thyroid  Muscles. — The  '  crico-thyroid '  is  a  short  and  strong 
muscle.  It  arises  from  the  side  of  the  cricoid  cartilage,  and  is  inserted 
into  the  lower  border  of  the  thyroid,  including  the  lesser  cornu.  Its  ac- 
tion is  to  stretch  the  vocal  cords.  It  does  this  by  depressing  the  thyroid 


Arytenoid  cartilage. 


Crieo-aiytenoid  joint.  —  £<5- 


Crico-thyroid  joint . . 


Thyroid  cartilage. 


Thyroid  cartilage  depressed. 

True  vocal  cord. 

True  vocal  cord  stretched. 


Crico-thyroid  muscle. 
Cricoid  cartilage. 


FIG.  80.— Diagram  showing  the  Action  of  the  Crico-thyroid  Muscle. 

cartilage,  the  arytenoid  cartilage  remaining  fixed.  Under  this  condition 
the  thyroid  cannot  be  depressed  without  increasing  the  distance  between 
the  attachments  of  the  vocal  cords,  as  shown  by  the  dotted  line  in  Fig. 
80.  Consequently  the  '  crico-thyroid,'  when  in  action,  must  elongate  the 
vocal  cords. 

Crico-arytenoidei    Postici. — Each    '  crico-arytenoideus    posticus' 
arises  from  the  posterior  part  of  the  cricoid  cartilage,  and  is  inserted  into 


Vocal  cord 

Thyroid  cartilage  . 
Cricoid  cartilage .  . 


Arytenoid  cartilage 


Elastic  ligament  .  , 
(.crico-arytenoid) 


Crico-arytenoideus 
Mentis. 


Ideal  pivot. 


Crico-arytenoideus 
posticus. 


FIG.  81.— Glottis  Dilated.    Muscles  dilating  it  represented  wavy. 

the  posterior  tubercle  of  the  arytenoid.     The  muscle  is  seen  in  action 
liy  wavy  lines)  in  Fig.  81.    Its  action  is  to  dilate  the  glottis.     It 


250  HUMAN    OSTEOLOGY. 

does  this  by  drawing  the  posterior  tubercle  of  the  arytenoid  toward  the 
mesial  line,  and  therefore  the  anterior  tubercle  from  the  mesial  line.  In 
this  movement  the  arytenoid  cartilage  rotates  upon  the  cricoid  as  upon 
a  pivot.  Moreover,  the  arytenoid  cartilage  is  a  lever  of  the  first  order; 
the  fulcrum  or  ideal  pivot  being  intermediate  between  the  power  at  the 
posterior  tubercle  and  the  weight  or  resistance  at  the  anterior.  The 
muscle  in  question  is  a  most  important  one.  It  is  a  muscle  of  inspira- 
tion. It  dilates  the  glottis  every  time  we  inspire.  During  expiration, 
when  the  glottis  is  restored  to  its  state  of  rest,  not  by  muscular  action, 
but  by  an  elastic  ligament,  the  '  crico-arytenoid,'  marked  in  Fig.  81, 
the  muscle  relaxes,  and  has  time  to  rest.  This  alternate  contraction  and 
relaxation  of  the  '  crico-arytenoidei  postici '  is  perpetually  going  on,  from 
the  first  moment  of  life  till  the  last. 

Crico-arytenoideus  Lateralis. — Each  '  crico-arytenoideus  lateralis ' 
arises  from  the  upper  border  of  the  cricoid  cartilage,  and  is  inserted  into 


Vocal  cord iWm  ^JIlBL^^. Thyrc-arytenoideus. 


Arytenoid     in  111 " 
Elastic  ligament .  .  . 


Crico-arytenoideus 
posticus. 

FIG.  82.— Glottis  Closed.    Muscles  closing  it  represented  wavy. 

the  posterior  tubercle  of  the  arytenoid.  Its  action  is  to  assist  in  closing 
the  glottis,  as  seen  in  Fig.  82.  It  does  this  by  rotating  the  arytenoid 
cartilage  in  a  way  directly  the  reverse  of  the  muscle  last  examined. 

Arytenoideus. — The  'arytenoideus'  muscle  arises  from  the  back  of 
one  arytenoid  cartilage,  and  is  inserted  into  the  back  of  the  other.  (Plate 
LVII.  Fig.  3.)  It  clasps  the  two  cartilages  together,  and  therefore  as- 
sists very  materially  in  closing  the  glottis.106 

105  Certain  muscular  fibres  in  the  aryteno-epiglottidean  folds  of  mucous  membrane 
assist  the  '  arytenoideus  '  and  the  '  crico-arytenoidei  laterales  '  in  closing  the  glottis. 
All  these  little  muscles  together  form,  as  Henle  has  shown,  a  '  sphincter'  of  the  glot- 
tis, a  highly  developed  and  complicated  homologue  of  the  single  and  simple  sphincter 
muscle  which  embraces  the  entrance  of  the  larynx  in  reptiles. 


THE    LARYNX.  251 

Thyro-arytenoidei. — Each  of  these  muscles  arises  from  the  angle 
of  the  thyroid,  and  is  inserted  into  the  front  surface  of  the  base  of  the 
arytenoid.  They  relax  the  vocal  cords,  since  they  tend  to  draw  together 
the  cartilages  to  which  they  are  attached.  More  than  this,  they  assist  in 
narrowing  the  glottis.  But  their  special  action  appears  to  be  that  of 
bringing  the  lips  of  the  glottis  parallel  to  each  other;  that  of  placing 
them,  in  fact,  in  the  '  vocalizing '  position.  The  glottis  must  be  made 
not  only  a  very  narrow  chink,  but  its  lips  must  be  brought  parallel  to 
each  other,  before  they  can  be  made  to  vibrate  by  the  stream  of  the  air, 
in  such  a  manner  as  to  produce  voice  or  song.  The  motions  of  the  glottis 
in  singing,  speaking,  breathing,  and  coughing  can  be  distinctly  seen  in 
the  laryngoscope. 

The  following  is  a  tabular  arrangement  of  the  action  of  the  muscles 
of  the  larynx: 

(  Crico-thyroidei stretch  the  vocal  cords  )  govern  the  pitch  of 

ANTAGONISTS    •{  }• 

(  Thyro-arytenoidei relax  the  vocal  cords     )  the  notes. 

Crico-arytenoidei  postici open  the  glottis  ) 

/  govern  the  opening 
ANTAGONISTS    •{  Crico-arytenoidei  laterales  l  doM  ^  glQtti8  V      rf  ^ 

Arytenoideus , J  ; 


THE  ANATOMY  OF  THE  EAR 

IN  describing  the  anatomy  of  this  intricate  and  delicate  organ,  a  general 
outline  of  its  structure  will  first  be  given,  and  afterward  the  details  of  its 
several  parts. 

General  Idea  of  the  Subject. — To  obtain  a  general  idea  of  the 
organ  of  hearing,  look  at  the  diagram,  Fig.  1,  Plate  LVIII.  In  this  is 
seen  the  elastic  fibro-cartilage  termed  the  '  pinna'  of  the  ear,  which  col- 
lects the  sonorous  undulations  of  the  air,  and  transmits  them  down  the 
passage  called  the  '  meatus  auditorius  externus.'  This  passage,  about  an 
inch  and  a  quarter  in  length,  is  a  little  contracted  in  the  middle,  where 
its  floor  is  a  little  raised.  It  is  closed  at  the  bottom  by  a  fibrous  membrane 
(membrana  tympani)  which  is  fixed  in  a  groove  in  the  bone,  is  placed 
obliquely,  and  stretched  in  all  respects  like  the  parchment  of  a  drum, 
except  that  its  outer  surface  is  a  little  concave. 

Tympanum. — On  the  inner  side  of  the  membrana  tympani  is  a 
small  chamber  in  the  substance  of  the  temporal  bone,  termed  the  '  tym- 
panum '  or  middle  ear.  This  chamber  is  filled  with  air,  which  is  admitted 
through  a  tube  (Eustachian  tube)  about  an  inch  and  a  half  long,  leading 
from  the  back  part  of  the  nostrils  into  the  front  part  of  the  tympanum. 
Thus  there  is  an  equilibrium  of  air  on  both  sides  of  the  membrana  tym- 
pani. In  fact,  the  Eustachian  tube  performs  the  same  office  for  the  ear 
as  the  hole  which  is  made  in  the  side  of  a  drum  for  the  necessary  purpose 
of  opening  a  communication  with  the  external  air.  Opposite  to  the 
Eustachian  tube,  that  is,  at  the  back  part  of  the  tympanum,  are  the  irregu- 
lar openings  of  the  mastoid  cells,  which  also  contain  air.  All  these  air  cavi- 
ties are  lined  by  a  continuation  of  the  mucous  membrane  which  lines  the 
passages  of  the  nose.  This  explains  the  degree  of  deafness  which  is  often 
produced  by  a  common  cold,  or  other  disease  of  the  throat:  the  Eusta- 
chian tube  being  temporarily  obstructed  by  the  swelling  of  its  lining 
membrane. 

Ossicula  Auditus.  Malleus,  Incus,  and  Stapes.— In  the  tym- 
panum itself  we  find  three  little  bones  (ossicula  auditus)  known  separately 


THE    ANATOMY    OF    THE   EAR.  253 

by  names  more  descriptive  of  their  shape  than  their  office — '  malleus/ 
'  incus/  and  '  stapes/  These  bones  are  connected  by  perfect  joints,  so  as 
to  form  a  continuous  chain,  surrounded  by  atmospheric  air,,  across  the  cav- 
ity of  the  tympanum;  and  the  mucous  membrane  is  reflected  over  them. 
The  handle  (manubrium)  of  the  malleus  at  one  end  of  the  chain  is  at- 
tached to  the  '  membrana  tympani/  and  the  foot-plate  of  the  stapes  at 
the  other  end  closes  the  '  fenestra  ovalis/  an  opening  on  the  inner  wall  of 
the  tympanum  leading  to  the  '  vestibule '  of  the  internal  ear.  Both  ends 
of  the  bony  chain  are  attached  to  membrane,  since  the  foot-plate  of  the 
stapes  does  not  exactly  fit  into  the  fenestra  ovalis;  membrane  intervening 
between  their  edges.  Moreover,  certain  little  muscles  are  attached  to  the 
bones,  and  slacken  or  tighten  the  membranes.  Besides  the  fenestra  ovalis, 
there  is  another  opening  in  the  inner  wall  of  the  tympanum,  called  the 
'  fenestra  rotunda/  It  leads  into  the  cochlea  and  is  closed  by  membrane. 

Internal  Ear. — The  internal  ear,  often  called,  on  account  of  its  in- 
tricacy, the  '  labyrinth/  consists  of  a  little  chamber  termed  the  '  vesti- 
bule/ the  three  '  semicircular  canals/  and  the  '  cochlea.'  All  these  parts 
are  embedded  in  the  petrous  portion  of  the  temporal  bone  like  passages 
cut  out  of  a  solid  rock.  Hence  the  great  difficulty  of  exploring  them. 
Bear  in  mind  their  relative  position.  The  '  vestibule '  is  in  the  middle, 
the  canals  are  behind,  and  the  cochlea  is  in  front. 

Vestibule. — The  vestibule  communicates,  behind,  with  the  five  open- 
ings of  the  semicircular  canals;  in  front,  with  the  cochlea;  on  the  outer 
side  with  the  tympanum  through  the  fenestra  ovalis  (occupied  by  the 
stapes);  and  on  the  inner  side  by  minute  apertures  with  the  meatus  audi- 
torius  internus,  through  which  the  auditory  nerve  enters  the  ear.  These 
apertures  transmit  those  branches  of  the  auditory  nerve  which  supply  the 
membranous  contents  of  the  vestibule  and  the  semicircular  canals. 

Cochlea. — The  cochlea,  so  named  from  its  resemblance  to  a  snail's 
shell,  is  an  exceedingly  curious  structure.  It  is  placed  so  that  the  base  of 
the  shell  corresponds  to  the  bottom  of  the  meatus  auditorius  internus, 
while  the  apex  points  forward  and  outward  toward  the  Eustachian  tube. 
It  is  formed  by  the  spiral  convolutions  of  two  gradually  tapering  tubes, 
or  rather  by  one  tube  separated  into  two  compartments  by  a  longitudinal 
septum  (lamina  spiralis),  composed  partly  of  thin  bone,  but  chiefly  of 
membrane.  In  the  diagram  the  course  of  the  septum  is  indicated  by  a 
dotted  outline.  This  septum  is  the  most  important  part  of  the  cochlea, 
because  the  auditory  nerve  expands  upon  it.  It  runs  all  through  the 


254  HUMAN    OSTEOLOGY. 

tube,  except  at  the  apex,  where  it  suddenly  terminates  in  a  curved  hook, 
and  leaves  an  aperture  (helicotrema),  so  that  the  two  portions  of  the 
tube  communicate.  One  portion  of  the  tube  (scala  vestibuli)  opens  into 
the  vestibule;  the  other  portion  (scala  tympani)  leads  into  the  tympanum 
through  the  'fenestra  rotunda/  This  last  foramen  is  open  only  in  the 
dry  bone;  in  the  recent  state  the  fenestra  rotunda  is  closed  by  the  '  mem- 
brana  tympani  secundaria/  which  therefore  has  the  air  of  the  tympanum 
on  the  one  side  and  the  fluid  in  the  cochlea  on  the  other.  The  central 
pillar  of  the  cochlea  round  which  the  tube  makes  two  and  a  half  turns  is 
called  the  'modiolus'  or  'axis.' 

Semicircular  Canals. — The  semicircular  canals  are  three  in  num- 
ber, and  are  called,  from  their  position,  '  superior/  '  posterior/  and  '  ex- 
ternal.' They  are  placed  in  planes  at  right  angles  to  each  other  like  the 
faces  of  a  cube.  Each  canal  forms  the  greater  part  of  a  circle,  and  opens 
at  each  end  into  the  vestibule.  There  are  only  five  openings,  since  two 
of  the  canals  have  an  opening  in  common.  Each  canal  has  a  dilatation 
at  one  end  termed  the  'ampulla';  this  makes  room  for  a  corresponding 
dilatation  of  the  membranous  canal  within  it,  upon  which  the  auditory 
nerve  expands.  The  '  ampulla/  therefore,  is  the  most  important  part  of 
each  canal. 

Uses  of  these  Excavations. — These  curious  and  elaborate  excava- 
tions in  the  petrous  bone  form  receptacles  for  a  fluid  in  which  floats  the 
delicate  membrane  destined  to  receive  the  terminal  filaments  of  the  audi- 
tory nerve.  This  membrane  is  the  very  essence  of  the  organ  of  hearing. 
It  is  to  the  ear  what  the  retina  is  to  the  eye.  In  the  vestibule  and  semi- 
circular canals  it  forms  a  continuous,  but  closed  sac,  which  copies  pretty 
accurately  the  shape  of  these  cavities,  without  being  in  contact  with  their 
bony  walls.  It  is  bathed  within  and  without  by  a  thin  albuminous  fluid. 
That  part  of  the  fluid  within  the  membrane  is  called  the  'endolymph'; 
that  without,  the  'perilymph/  or  'liquor  Cotunuii.'  Within  the  cochlea 
the  membrane  is  arranged  in  a  different  manner.  It  forms  here  the 
greater  part  of  the  '  lamina  spiralis/  and  encloses  a  third  scale  or  spiral 
passage,  the  '  canalis  membranacea/  or  '  canalis  cochleae/  absent  in  the 
macerated  labyrinth.  Inside  this  membranous  canal  is  a  series  of  cellular 
bodies  arranged  in  a  very  complicated  manner,  and  known  as  the  '  organ 
of  Corti.'  The  membranous  canal  is  filled  with  endolymph;  the  cavities 
of  the  scala  vestibuli  and  scala  tympani  are  occupied  by  perilymph. 

The  auditory  nerve  enters  the  ear  through  the  meatus  auditorius  in- 


THE    ANATOMY    OF    THE    EAR.  255 

ternus.  At  the  bottom  of  this  passage  are  a  multitude  of  small  foramina, 
which  transmit  the  minute  subdivisions  of  the  nerve  to  their  respective 
destinations.  Some  are  distributed  upon  the  sac  in  the  vestibule;  some 
upon  the  dilatations  (ampullae)  of  the  membranous  semicircular  canals; 
others  run  down  the  axis  of  the  cochlea,  and  are  distributed  to  the  struct- 
ures within  the  canalis  membranacea. 

Probable  Function  of  these  several  Parts. — Now  for  the  ex- 
planation, usually  received,  of  the  function  of  these  several  parts.  The 
waves  of  sound,  collected  by  the  cartilage  of  the  ear,  pass  down  the  ex- 
ternal auditory  passage,  strike  upon  the  membrana  tympani,  and  cause  it 
to  vibrate.  These  vibrations  are  carried  by  the  little  bones  across  the 
tympanum  to  the  membrane,  which  closes  the  '  fenestra  ovalis,'  or  open- 
ing into  the  vestibule.  This  membrane,  thus  thrown  into  vibration, 
communicates  motion  to  the  fluid  in  the  labyrinth;  the  filaments  of  the 
auditory  nerve  receive  the  impression  and  transmit  the  sensation  of  sound 
to  the  brain.  The  vibrations  of  the  membrana  tympani  excite  corespond- 
ing  vibrations  in  the  air  within  the  cavity  of  the  tympanum,  which  again 
communicates  them  to  the  membrane  closing  the  fenestra  rotunda,  and 
through  this  they  reach  the  cochlea.  Here  we  have  a  ready  explanation 
of  the  use  of  the  fenestra  rotunda  and  the  membrane  closing  it:  that  is, 
we  have,  interposed  between  air  and  a  fluid,  a  tense  membrane,  which  is 
the  very  best  medium  for  transmitting,  with  increased  intensity,  vibra- 
tions from  one  to  the  other. 


After  the  preceding  sketch  of  the  anatomy  of  the  ear,  proceed  now  to 
a  more  minute  examination  of  its  component  parts.  It  is  taken  for 
granted  that  the  learner  is  already  familiar  with  the  anatomy  of  the  tem- 
poral bone  described  at  page  47. 

Meatus  Auditorius  Externus. — This  passage  leads  to  the  mem- 
brana tympani.  Its  outer  third  is  formed  by  a  tubular  continuation  of 
the  cartilage  of  the  ear;  its  inner  two-thirds  by  the  osseous  canal  in  the 
temporal  bone.  The  cartilaginous  part  is  united  by  fibrous  membrane  to 
the  rough  margin  of  the  processus  auditorius.  The  cartilage,  however, 
does  not  itself  form  a  complete  tube;  there  is  a  slight  deficiency  at  the 
upper  part,  completed  by  fibrous  membrane.  There  are  also  one  or  two 
vertical  fissures  in  the  cartilage.  These  breaks  in  the  cartilage  give 


256  HUMAN    OSTEOLOGY. 

greater  freedom  of  motion;  they  are  interesting  practically,  as  explaining; 
how  collections  of  matter  in  the  parotid  gland  sometimes  make  their  way 
into  the  meatus  auditorius. 

Length. — The  length  of  the  meatus,  measured  from  the  middle  of 
its  external  orifice  to  the  middle  of  the  membrana  tympani,  is  about  one 
inch  and  two  or  three  lines.  The  anterior  wall  is  about  one-fourth  of  an 
inch  longer  than  the  posterior,  in  consequence  of  the  oblique  direction  of 
the  membrana  tympani. 

Direction. — The  direction  of  the  meatus  is  inward  and  forward.  It 
describes  a  slight  curve  with  the  concavity  downward.  Besides  this  gen- 
eral curve,  the  cartilaginous  part  is  slightly  curved  with  the  concavity 
forward,  and  the  osseous  part  with  the  concavity  backward.  Altogether, 
the  meatus  has  such  a  curious  shape  that  it  cannot  be  well  understood 
without  looking  at  a  cast  of  it.  Every  surgeon  knows  how  difficult  it  is. 
to  see  the  whole  of  the  membrane  of  the  tympanum  at  one  view:  one  can 
seldom  see  more  than  a  part  of  it,  however  much  the  ear  be  dilated  and 
pulled  so  as  to  straighten  the  outer  curve.  The  narrowest  part  of  the 
meatus  is  about  the  middle.  Beyond  this  point  we  ought  not  to  intro- 
duce the  speculum. 

Meatus  in  the  Infant. — The  preceding  description  of  the  external 
auditory  meatus  refers  to  its  condition  in  the  adult.  In  infancy,  the 
meatus  is  extremely  short  on  account  of  the  non-development  of  the  bony 
portion,  which  at  this  period  is  a  mere  ring  (see  '  Temporal  Bone').  The 
membrana  tympani,  too,  is  almost  on  the  plane  of  the  base  of  the  skull, 
this  is  a  conspicuous  feature  in  the  cranium  of  a  new-born  child,  where 
the  membrane  absolutely  lies  on  the  floor  of  the  meatus.  It  is  most  im- 
portant that  a  surgeon  should  bear  these  facts  in  mind  when  examining 
the  ears  of  very  young  children. 

Insects  sometimes  find  their  way  down  the  meatus  and  cause  intense 
pain.  An  instance  is  related  by  Wilde108  which  is  worth  giving,  if  only 
to  show  how  to  dislodge  them:  '  I  remember  being  out  shooting  with  a 
friend,  who,  suddenly  exclaiming,  "  Oh,  an  earwig!"  and  throwing  aside 
his  gun,  fell  on  the  ground,  making  the  most  piteous  groans,  and  rolling 
about  in  agony.  Suspecting  that  some  insect  had  got  into  his  ear,  I  pro- 
cured some  water  from  a  ditch,  and  poured  it  into  the  meatus.  While 
watching  the  result,  a  little  animal,  well  known  among  anglers  as  the 
hawthorn  fly,  crept  out,  and  my  friend  was  instantly  relieved.' 
106  Wilde,  'Aural  Surgery, '  p.  178. 


PLATE  LVIII. 


Kittens, 

Merabrano_iy  rn^ani, . 


.Tymoajium* 

EustacKi«tn  tube* 


D  ia^ram.  o£  fKe  Ear* 


[Opening  into  Masloid  cells, 
Jerestra  rctunSsu 


nestra  ova-lisi 


Canal  forHensor.tympam 


UiustacHiecn  tube , 


Groove  ixr5"MJem"bran  a  lym  pan  i  \\ 
foramen  cViorclas...-*'  : 

JPyrarnltl -•'' 

•for    Stapeiiius;, 

Prepara,tion  to  shew  inner* -wall  of  tympaTTunn. 


THE    ANATOMY    OF   THE   EAR.  257 

Membrana  Tympani.— The  membrana  tympani  is  a  thin,  semi- 
transparent,  fibrous  membrane,  of  a  greyish  color,  placed  very  obliquely 
at  the  bottom  of  the  meatus  auditorius  externus.  Its  direction  is  down- 
ward, forward,  and  inward.  This  obliquity  increases  the  extent  of  sur- 
face; so  that  every  wave  of  sound,  reflected  down  the  meatus,  must  fall 
upon  it.  Its  circumference,  which  is  nearly  circular,  is  fixed  into  a  groove 
in  the  bone,  so  fine  that  it  might  have  been  traced  with  the  point  of  a 
needle.  (Plate  LVIII.  Fig.  2.)  This  groove,  however,  does  not  form  a 
complete  circle:  it  is  deficient  at  the  upper  part,  where  the  membrana 
tympani  is,  more  obviously  than  elsewhere,  continuous  with  the  skin  lin- 
ing the  meatus. 

The  membrana  tympani  is  not  flat,  like  the  parchment  of  a  drum,  but 
slightly  conical,  with  the  apex  toward  the  tympanum.  This  shape  seems 
given  to  it  by  the  handle  of  the  malleus,  which  draws  the  membrane  a 
little  inward.  The  handle  of  the  bone  can  be  seen  in  the  living  subject, 
like  a  thin  white  streak,  which  is  not  quite  vertical,  but  inclines  slightly 
backward. 

Many  times  a  hole  exists  in  the  upper  part  of  the  membrane,  even  in 
cases  where  there  is  no  obvious  defect  of  hearing  during  life.  This  suffi- 
ciently explains  why  some  persons  who  are  not  deaf  can  blow  the  smoke  of 
tobacco  through  the  ear  as  well  as  through  the  nose. 

Structure  of  the  Membrana  Tympani. — Thin  as  it  is,  the  mem- 
brana tympani  is  very  strong.  It  has  three  strata:  an  outer  stratum  of 
cuticle;  a  middle,  fibrous,  on  which  its  strength  chiefly  depends;  and  an 
internal,  mucous.  (Plate  LX.  Fig.  3.)  The  middle  stratum  is  composed 
of  fibres  radiating  and  circular,  but  no  longer  considered  muscular.  It  is 
this  coat  which  is  fixed  into  the  bony  groove,  and  contains  in  its  very 
substance  the  handle  of  the  malleus.  The  dermal  stratum  is  composed  of 
an  extremely  thin  layer  of  the  true  skin,  continuous  with  that  lining  the 
meatus  auditorius  externus.  The  mucous  lining  is  continuous  with  the 
lining  of  the  tympanum.  The  membrane  is  well  supplied  with  blood  by 
arteries  derived  from  the  stylo-mastoid  and  the  tympanic  branch  of  the 
internal  maxillary. 

Tympanum,  or  Middle  Ear. — We  need  not  repeat  what  has  been 
said  already  about  the  tympanum,  but  pass  on  to  examine  what  is  to  be 
seen  on  its  several  aspects,  namely:  its  external  aspect,  its  internal,  its 
anterior  and  posterior,  its  superior  and  its  inferior. 

External   Aspect. — On  the  outer  aspect  of  the  tympanum  there 
17 


258  HUMAN    OSTEOLOGY. 

is  the  bottom  of  the  meatus  auditorius,  closed  by  the  membrana 
tympani. 

Internal  Aspect. — On  the  inner  aspect  of  the  tympanum  (Plate 
'LVIII.  Fig.  2)  are  seen — 1.  The  fenestra  ovalis  leading  to  the  vestibule: 
this  is  open  in  the  dry  bone,  but  closed  in  the  recent  state  by  the  base  of 
the  stapes  which  is  held  to  the  margins  of  the  fenestra  by  ligamentous 
fibres.  The  fenestra  ovalis  looks  outward  toward  the  membrana  tympani. 
2.  The  fenestra  rotunda:  this,  in  the  recent  state,  is  also  closed  by  mem- 
brane (membrana  tympani  secundaria);  in  the  dry  bone  it  leads  to  the 
tympanic  scale  of  the  cochlea,  and  also  into  the  vestibule;  but  the  fenes- 
tra does  not  communicate  with  the  vestibule  in  the  perfect  state.  The 
fenestra  rotunda  looks  almost  directly  backward.  3.  The  promontory: 
this  is  formed  by  the  bulging  of  the  first  turn  of  the  cochlea;  its  surface 
is  marked  by  grooves  for  the  ramifications  of  Jacobson's  nerve. 

Anterior  Aspect.— On  the  anterior  aspect  of  the  tympanum,  we  have 
— 1.  The  bony  canal  for  the  '  tensor  tympani '  (in  the  drawing,  this  canal 
is  cut  open).  Just  before  its  termination  in  front  of  the  fenestra  ovalis, 
the  canal  makes  a  sudden  curve  outward,  in  order  to  form  a  little  pulley 
for  the  tendon  of  the  muscle  within.  In  most  bones  this  part  of  the 
canal  is  broken,  and  has  the  appearance  of  a  little  spoon;  for  this  reason, 
it  is  called  the 'processuscochleariformis.'  2.  The  Eustachian  tube.  3. 
The  orifice  of  the  Glaserian  fissure  which  transmits  the  '  laxator  tympani ' 
and  the  chorda  tympani  nerve.  In  about  five  specimens  out  of  six,  the 
chorda  tympani  runs  through  a  little  canal,  close  to,  and  a  little  above 
the  Glaserian  fissure;  but  this  '  canal  of  Huguier,'  as  it  has  been  termed, 
is  of  no  practical  moment,  and  hardly  deserves  a  new  name. 

Posterior  Aspect. — On  the  posterior  aspect  of  the  tympanum,  are — 
1.  The  opening  into  the  mastoid  cells.  2.  The  pyramid — a  small  pro- 
jection containing  a  canal,  about  the  size  of  a  bristle,  which  lodges  the 
'  stapedius  muscle/  At  the  base  of  the  pyramid  (but  within  it)  are  two 
minute  canals  which  transmit,  the  one  an  artery,  the  other  a  nerve,  to 
the  stapedius.  The  pyramid  is  always  supported  by  a  minute  bony 
column,  which  extends  like  a  flying  buttress  from  its  apex  to  the  promon- 
tory. 3.  The  foramen  chordae,  'iter  chordae  postering.'  This  minute 
foramen  is  a  little  below  the  level  of  the  pyramid,  and  close  to  the  groove 
for  the  attachment  of  the  membrana  tympani.  Introduce  a  bristle  into 
it,  and  you  find  that  it  leads  into  the  '  aqueductus  Fallopii.'  It  transmits 
the  chorda  tympani  nerve.  This  nerve  is  a  branch  of  the  facial  (which, 


THE    ANATOMY    OF    THE    EAR.  259 

remember,  is  contained  in  the  '  aqueductus  Fallopii ' :  see  Plate  LX.  Fig. 
4).  It  comes  up  through  the  foramen  chordae,  runs,  not  across  the  tym- 
panum, but  across  the  membrana  tympani,  outside  the  mucous  membrane, 
between  the  handle  of  the  malleus  and  the  long  process  of  the  incus;  it 
leaves  the  membrane  through  the  Glaseriun  fissure  (or  through  a  distinct 
canal)  and,  joining  the  gustatory,  eventually  goes  to  the  submaxillary 
ganglion. 

Superior  Aspect. — On  the  superior  aspect  of  the  tympanum  is  a 
thin  plate  of  bone  which  separates  the  cavity  of  the  tympanum  from  that 
of  the  cranium.  This  is  an  important  relation.  For  it  shows  how  readily 
inflammation  might  spread  from  the  tympanum  to  the  base  of  the  brain. 

Inferior  Aspect. — The  inferior  aspect,  or  floor  of  the  tympanum, 
is  formed  by  the  jugular  fossa,  which  lodges  the  jugular  vein.  A  little 
in  front  of  this  fossa  is  the  canal  for  the  carotid  artery,  which  is  sepa- 
rated from  the  tympanum  only  by  a  thin  scale  of  bone.  The  vicinity  of 
these  great  vessels  explains  the  sudden  and  profuse  haemorrhage  which 
sometimes,  though  rarely,  occurs  from  the  ear  when  diseased.  Professor 
Porter  speaks  of  blood  gushing  from  the  ear  with  a  rapidity  such  as  he 
never  witnessed  in  a  surgical  operation. 10T  Ulceration  had  extended  into 
the  carotid  artery. 

In  another  case  of  sudden  and  profuse  bleeding  from  the  ear,  Mr. 
Syme  tied  the  carotid  artery.108  The  patient  died.  He  however  tied  the 
carotid  in  another  similar  case  in  which  the  patient  recovered.  Dissec- 
tion discovered  that  the  blood  came  from  the  lateral  sinus,  near  the  jugu- 
lar fossa,  the  thin  bony  septum  between  that  fossa  and  the  tympanum 
having  been  destroyed  by  ulceration.  Looking  at  the  proximity  of  these 
large  vessels,  there  is|^o  wonder  that  bleeding  from  the  ear,  after  injury 
to  the  head,  makes  one  suspect  the  existence  of  a  fracture  through  the 
tympanum. 

In  the  floor  of  the  tympanum  there  are  a  number  of  minute  holes, 
among  which  especially  note  one,  the  upper  opening  of  the  canal  for 
Jacobson's  nerve.  The  lower  opening  of  the  canal  is  at  the  base  of  the 
skull,  on  the  little  crest  of  bone  which  separates  the  jugular  fossa  from  the 
carotid  canal.  The  nerve  in  question  is  a  branch  of  the  glosso-pharyngeal. 
It  enters  the  tympanum,  and  ramifies  upon  the  promontory,  forming 

'<"  Graves's  '  Clinical  Medicine.'  vol.  i. 

108  'Edinburgh  Monthly  Journal, '  No.  III.;  '  Edinb.  Med.  and  Surg.  Journal,' 
No.  CXV.  p.  319. 


260  HUMAN    OSTEOLOGY. 

what  is  called  the  '  tympanic  plexus.'  It  supplies  the  mucous  membrane 
of  the  tympanum.  Its  principal  branches  are  generally  indicated  by 
grooves  made  for  their  passage  on  the  promontory.  In  a  preparation 
where  there  appeared  to  be  neither  groove  nor  nerve,  the  nerve  was 
subsequently  found  lodged  in  a  complete  bony  canal  within  the  pro- 
montory. 

Aqueductus  Fallopii. — The  '  aqueductus  Fallopii/  or  canal  for 
the  facial  nerve,  which  supplies  all  the  muscles  of  expression  of  the  face 
(Plate  LIX.  Fig.  1.),  commences  at  the  bottom  of  the  meatus  auditorius 
internus;  it  runs  for  a  short  distance  outward,  then  turns  horizontally  back- 
ward along  the  inner  wall  of  the  tympanum,  just  above  the  fenestra  ovalis, 
and,  lastly,  descending  behind  the  tympanum,  emerges  at  the  stylo-mas- 
toid  foramen.  Its  course  suggests  how  liable  the  nerve  is  to  be  injured 
in  fracture  through  the  temporal  bone,  or  in  disease  of  the  ear.  While 
in  this  canal  the  nerve  sends  off  three  important  branches,  all  to  ganglia. 
These  are  shown  in  Plate  LX.  Fig.  4.  The  first  branch,  the  greater 
petrosal,  or  Vidian,  runs  down  the  hiatus  Fallopii  to  the  spheno-palatine 
ganglion;  the  second,  or  lesser  petrosal,  goes  to  the  otic  ganglion;  the 
third,  or  chorda  tympani,  runs  with  the  gustatory  nerve  to  the  submaxil- 
lary  ganglion.  Two  less  important  nerves  are  also  given  off  from  the 
facial  in  the  aqueductus  Fallopii,  namely,  the  external  petrosal  which 
communicates  with  the  sympathetic  on  the  middle  meningeal  artery,  and 
the  nerve  to  the  stapedius  muscle. 

The  objects  seen  on  the  inner  wall  of  the  tympanum  may  be  better 
understood  in  the  following  tabular  form: — 


-  21 

Mastoid  cells.  /    r^T^Pyi  Canal  for  tens°r  tympani.  \  , 

Pyramid  for  stapedius.  /      v^v-n     £      }  Eustachian  tube. 

Foramen  chord^T  /    ;  ^^Jft^-.-J  Glaserian  fissure. 


Little  Bones  in  the  Tympanum.— The  three  little  bones  in  the 
tympanum  are  drawn  larger  than  natural,  but  in  their  proper  relative 
position,  Plate  LIX.  Figs.  2,  3,  4,  and  5.  In  Fig.  3,  you  are  supposed 
to  be  looking  at  them  from  the  meatus  auditorius;  in  Fig.  2,  from  the 


PLATE  LIX. 


s  1?  all  op  ii 
Hiafcns'Fallopn 


Groove  for  JseobsonsUerve, 


Carotid  canal. 


Incus,          TfoiHeu?. 
3"hort  process. 
../.Stapes.  $tapes £ 


' Outline  of  V'-.  ./ "Handle. 

Inner  view,  Mem:tympani.J     *•. ••'' 


Base 


THE    ANATOMY    OF   THE   EAR.  261 

inside  of  the  tympanum.  The  dotted  line  in  each  figure  is  intended  to 
represent  the  outline  of  the  membrana  tympani. 

Malleus. — The  malleus  or  hammer  presents  a  head,  a  neck,  and  a 
handle  (manubrium).  The  '  head '  is  the  large  round  part  above  the  mem- 
brana tympani.  It  articulates  posteriorly  with  the  incus  by  means  of  a 
concavo-convex  joint,  crusted  with  cartilage  and  provided  with  a  synovial 
membrane.  The  '  neck '  is  the  narrow  portion  between  the  head  and  the 
handle.  From  the  front  of  the  neck  springs  the  '  long  process '  or  '  pro- 
cessus  gracilis '  which  runs  down  the  Glaserian  fissure  and  gives  insertion 
to  the  '  laxator  tympani/  In  infants  this  '  processus  gracilis'  may  be  re- 
moved whole,  together  with  the  rest  of  the  malleus;  but,  in  the  adult,  it 
is  adherent  to  the  temporal  bone  and  cannot  be  extracted  entire.  The 
handle  or  '  manubrium '  descends  nearly  perpendicularly  from  the  neck. 
Near  the  root  of  the  handle  is  a  little  projection  called  the  '  short  process,' 
which  presses  against  the  upper  part  of  the  membrana  tympani.  The 
handle  itself  terminates  in  a  slightly  flattened,  outwardly  curved  extremity, 
a  little  below  the  centre  of  the  membrane.  On  the  inner  side  of  ihe  handle 
and  below  the  processus  gracilis,  is  inserted  the  '  tensor  tympani.' 

Right  or  Left  ? — This  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body,  if  he  hold  the  articular  surface 
backward,  the  handle  downward,  and  the  processus  brevis  outward. 

Incus. — The  incus,  or  anvil,  lies  behind  the  malleus.  It  has  a  body, 
a  short,  and  a  long  process.  The  body  is  convex,  placed  above  and 
behind  the  membrana  tympani,  and  has  a  concavo-convex  surface  which 
articulates  with  the  head  of  the  malleus.  The  '  short  process '  extends 
horizontally  backward  into  the  mastoid  cells,  and  is  fixed  there  by  a  liga- 
ment. The  'long  process'  descends  nearly  vertically,  parallel  to  the 
handle  of  the  malleus,  and,  like  it,  is  a  little  convex  outwardly.  Toward 
the  extremity  it  suddenly  turns  up  and  supports,  on  a  narrow  pedicle, 
the  orbicular  process  formerly  termed  '  os  orbiculare '  (Fig.  5). 

Right  or  Left  ? — This  bone  will  be  in  the  same  position  as  the  cor- 
responding one  in  the  student's  body,  if  he  hold  the  short  process  back- 
ward, the  long  process  downward  and  inward. 

Os  Orbiculare. — The  little  '  os  orbiculare,'  considered  by  some  as  a 
separate  bone,  is  always  anchylosed  in  the  adult  to  the  long  process  of 
the  incus;  but  it  is  connected  with  the  stapes  by  a  very  distinct  joint. 

The  Stapes.— The  stapes,  or  stirrup,  is  placed  horizontally,  with 
the  base  in  the  fenestra  ovalis.  It  has  a  head,  a  neck,  two  '  crura '  or 


262  HUMAN    OSTEOLOGY. 

branches,  and  a  base  or  foot-plate.  The  head  articulates  by  a  concave 
surface  with  the  orbicular  process  of  the  incus.  The  neck  gives  attach- 
ment behind  to  the  'stapedius.'  (Plate  LX.  Fig.  2.)  The  anterior 
branch  of  the  stirrup  is  shorter  and  less  curved  than  the  posterior;  both 
are  grooved  on  their  concave  sides,  and  the  interval  is  closed  by  a  mem- 
brane. It  has  been  stated  that  the  groove  in  the  cms  forms  half  an  Haver- 
sian  canal,  lodging  a  small  vessel.10'  The  '  base '  is  similar  in  form  to  the 
fenestra  ovalis,  which  it  nearly  fills,  and  their  margins  are  united  by  an 
annular  ligament.  The  lower  border  of  the  base  is  straighter  than  the 
upper,  and  its  anterior  extremity  is  the  sharpest. 

Right  or  Left  ? — This  bone  will  be  in  the  same  position  as  the 
corresponding  one  in  the  student's  tympanum,  if  he  hold  the  base  inward, 
its  straighter  side  downward,  and  the  shorter  limb  forward. 

Ossification. — All  the  bones  in  the  tympanum  are  ossified  and  well 
developed  at  birth.  The  ear-bones  of  a  new-born  infant  and  those  of  the 
giant  O'Brien,  seven  feet  seven  inches  high,  are  very  nearly  the  same  size. 
Of  the  four  bones,  the  stapes  is  the  most  essential  to  hearing.  Disease  may 
destroy  the  others,  and  still  the  patient  may  hear:  but  when  the  stapes 
falls  out,  the  fluid  in  the  vestibule  escapes,  and  inevitable  deafness  results. 

Little  Muscles  moving  the  Bones  in  the  Tympanum.— There 
are  two  well-marked  muscles  with  distinct  tendons  attached  to  the  bones 
in  the  tympanum,  namely,  the  tensor  tympani  and  the  stapedius.  (Plate 
LX.  Figs.  1,  2.)  The  '  laxator  tympani '  is  still  described  as  a  muscle  by 
some  anatomists,  though  its  muscular  structure  is  doubted  by  many. 

Tensor  Tympani. — The  '  tensor  tympani '  is  a  well-marked  muscle. 
It  arises  from  the  apex  of  the  petrous  bone,  and  from  the  cartilage  of  the 
Eustachian  tube,  and  is  inserted  into  the  handle  of  the  malleus,  just  be- 
low the  processus  gracilis.  The  muscle  is  lodged  in  the  bony  canal  running 
above  and  parallel  with  the  Eustachian  tube;  and  when  its  tendon  reaches 
the  end  of  the  canal,  which  forms  an  elbow,  it  is  reflected  at  a  right  angle 
to  reach  its  insertion.  From  origin  to  insertion  the  muscle  is  enclosed 
in  a  strong  fibrous  sheath.  The  tendon  slides  within  the  sheath,  and  has 
asynovial  membrane. 

Laxator  Tympani. — The  '  laxator  tympani '  arises  from  the  spine 
of  the  sphenoid  bone,  runs  up  the  Glaserian  fissure,  and  is  inserted  into 
the  processus  gracilis  of  the  malleus.  Like  the  last  muscle,  it  is  sur- 

109  '  Beitrage  zur  Anatomic  des  Steigbilgels, '  Archiv  ftir  Ohrenheilkunde,  vol.  v. 

Eysell. 


Laxator  t\ 


..Semicircular  canals . 

.Malleus 

icus 

..Cochlea.. 


;?lfc^rtvmpan^^-£^taaKkn  tube. 


.Kalleus. 


.Te  nsor  tytnpaovi 
Cut'icularlav? 
LaxaboriympaTii 


.Greater  petrosal  orVidian  nerve, 
'  .Lesser  petrosal  nerve 

— J  [• 


nerve. 
L.5pheno -palatine  oan^lion- 


THE    ANATOMY    OF    THE    EAR.  263 

rounded  by  a  sheath.  Whilst  there  is  no  doubt  whatever  about  the  mus- 
cularity of  the  '  tensor  tympani/  many  modern  anatomists  believe  the 
'  laxator  tympani '  to  be  a  ligament. 

Stapedius. — The  '  stapedius '  arises  in  the  canal  of  the  pyramid.  Its 
little  tendon,  coming  oat  of  the  canal  at  the  apex,  is  reflected  outward, 
and  inserted  into  the  posterior  part  of  the  neck  of  the  stapes.  Anato- 
mists are  not  agreed  about  the  precise  use  of  the  stapedius.  One  of  its 
actions  would  appear  to  be  to  tilt  the  steps  backward,  and  thus  diminish 
the  pressure  upon  the  fluid  in  the  vestibule. 

The  internal  ear  or  labyrinth,  comprising  the  vestibule,  semicircular 
canals,  and  cochlea,  should  now  be  examined.  And  first  of  the  vestibule, 
entered  through  the  'fenestra  ovalis.' 

Vestibule. — The  vestibule  is  of  an  ovoid  form,  measuring  about  ^th 
of  an  inch  in  its  long  diameter,  and  rather  less  in  its  short.     Posteriorly  it 
receives  the  five  openings  of  the  semicircular  canals  and  the  opening  of 
the  '  aqueductus  vestibuli ';  anteriorly,  and  at  its  lower  part,  is  the  open- 
On  the  inner  j  Fovea  hemispherica  for  saccule 
wall.         I  Fovea  hemielliptica  for  utricle 
Superior  semicircular  canal 

External  semicircular  canal 
Aqueductus  vestibuli. 

Posterior  semicircular  canal 

(  Fenestra  ovalis 

Outer  wall.-(  Opening  of  vestibular  scale  of  cochlea 

(  Opening  of  tympanic  scale  of  cochlea 

FIG.  84.— Diagram  of  the  Right  Vestibule,  and  the  Openings  into  it. 

ing  into  the  vestibular  scale  of  the  cochlea;  on  its  external  wall  is  the 
'  fenestra  ovalis.'  In  all,  then,  there  are  eight  openings  into  the  vestibule. 
The  internal  wall  of  the  vestibule  corresponds  with  a  part  of  the  bottom 
of  the  '  meatus  auditorius  internus.'  On  this  inner  wall,  as  shown  in 
Plate  LXI.  Fig.  3,  are  two  slight  depressions  separated  by  a  bony  ridge. 
The  upper  is  called  the  '  fovea  hemielliptica/  and  lodges  the  utricle;  the 
lower,  or  'fovea  hemispherica/  lodges  the  saccule.  The  ridge  dividing 
these  'foveae'  is  known  as  the  'crista  vestibuli.'  The  utricle  and  the 
saccule,  as  will  be  seen,  are  distinct  parts  of  the  membranous  labyrinth. 
The  fovese,  as  well  as  the  crista  vestibuli,  are  riddled  with  minute  fo- 
ramina, only  visible  with  a  lens,  through  which  the  filaments  of  the  audi- 
tory nerve  enter  the  vestibule.  The  vestibule  and  its  eight  openings  are 
represented  in  the  annexed  diagram,  Fig.  84. 


264  HUMAN    OSTEOLOGY. 

Semicircular  Canals. — The  three  semicircular  canals  are  called, 
according  to  their  position,  the  '  superior/  the  *  posterior '  (both  vertical) 
and  the  'external'  (horizontal).  The  superior  canal  crosses  the  petrous 
bone  at  right  angles,  and  stands  out  in  relief  on  its  anterior  surface.  Its 
'  ampulla '  is  at  the  outer  orifice.  The  posterior  canal  is  the  longest  of 
the  three.  It  runs  parallel  with  the  posterior  surface  of  the  petrous  bone, 
and  makes  a  little  relief  just  above  the  aqueductus  vestibuli.  Its  '  am- 
pulla' is  at  the  lower  orifice;  its  upper  orifice  joins  the  narrow  end  of  the 
superior  canal.  The  external  canal  is  the  smallest  of  the  three;  it  lies 
horizontally  in  the  petrous  bone  behind  the  superior  and  external  to  the 
posterior  canal;  its  convexity  is  directed  backward.  Its  ampulla  is  at  its 
outer  orifice. 

Cochlea. — The  cochlea  is  so  placed  that  its  base  is  at  the  bottom  of 
the  meatus  auditorius  internus,  where  it  receives  filaments  from  the  audi- 
tory nerve.  Its  apex  is  directed  forward  and  outward  close  to  the  canal 
for  the  tensor  tympani.  It  makes  two  turns  and  a  half,  which  run  from 
left  to  right  in  the  right  ear,  and  from  right  to  left  in  the  left,  round  the 
central  axis  termed  the  '  modiolus.'  Its  first  turn,  bulging  into  the  tym- 
panum, makes  the  'promontory.'  The  outer  wall  of  the  coil  is  composed 
of  a  lamella  of  very  hard  bone,  like  the  semicircular  canals:  the  inner  wall 
is  also  formed  of  compact  bone,  but  the  interior  of  the  '  modiolus '  is  spongy. 
The  last  half-turn  presents  peculiarities,  and  the  best  way  to  examine 
them  is  to  remove  the  '  cupola '  or  rounded  apex  of  the  cochlea,  as  seen  in 
Plate  LXI.  Fig.  4.  The  last  turn  forms  a  kind  of  half -funnel  (infundib- 
ulum).  Into  the  apex  of  this  funnel,  which  is  continuous  with  the  modi- 
olus, there  opens  a  canal  which  runs  through  the  centre  of  the  modiolus. 
Round  the  free  border  of  the  half-funnel  projects  the  hook-like  termi- 
nation (hamulus)  of  the  lamina  spiralis.  All  this  is  seen  only  in  the  dry 
bone.  In  the  recent  state  there  would  be  simply  the  aperture  of  com- 
munication (helicotrema),  between  the  two  scales  of  the  cochlea. 

The  tympanic  scale  runs  on  that  side  of  the  lamina  spiralis  which 
looks  toward  the  base  of  the  cochlea.  Near  the  beginning  of  that  scale  is 
the  minute  termination  of  the  aqueductus  cochleae.  (Plate  LXI.  Fig.  3.) 

Bony  Lamina  Spiralis. — The  bony  lamina  spiralis,  the  only  por- 
tion of  the  most  essential  part  of  the  cochlea  which  can  be  seen  in  the 
dry  bone,  is  shown  in  Fig.  85.  It  commences  at  the  lower  part  of  the 
vestibule  immediately  above  the  fenestra  rotunda.  (Plate  LXI.  Fig.  3.) 
From  this,  which  is  its  broadest  part,  it  gradually  diminishes  in  breadth 


Postf  Semicircular  canals 

•'    rr  ' 

,.  ;    •    !      .Aqueductus  "Fallopii 
.CocHlea. 


'•Canal  for  Carotid  artery. 


'Tenestra.  ovalis. 
Fenestrst  rotunda. 


FoVealiemiellipticaL., 
"Fov  e  a.  "K  eyy>  Vsioh  erica. 


'-'  '  Fenest-a  rotunda  ^^SSS^^P"  ''vAqueoluctus  vesfciliuli 

LamiTiaj 
,5ernicircu1ar  canals  and  CocMea  cut  open. 

Vestibule  opened  te  s>iew  its  inner  wall . 


ntre  of  modiol^s.i^ijj HaTnuiug  of  Lamina  sp.ir&Ti9. 

Apex  of  Cochlea, 


THE    ANATOMY    OF    THE    EAR.  265 

as  it  winds  round  the  axis  into  the  apex  of  the  cochlea,  never  reaching 
more  than  half  across  the  tube,  and  it  finally  terminates  as  a  little  hook 
(hamulus)  in  the  funnel  of  the  last  coil.  On  the  concave  side  of  this 
hook  is  situated  (in  the  recent  state)  the  helicotrema  or  aperture  of  com- 
munication between  the  two  scales.  Examined  with  a  lens,  both  surfaces 
of  the  lamina  spiralis  will  be  seen  to  be  furrowed  by  canals  which  give 
passage  to  the  nerves  before  they  reach  the  membranous  part  of  the  sep- 
tum. It  is  composed  of  two  very  delicate  and  brittle  plates  which  sepa- 
rate from  each  other  at  the  axis.  In  the  tympanic  scale  are  seen  the  ori- 
fices of  the  canals  just  alluded  to;  they  are  separated  by  little  columns  of 

Cupola - 

Hook  of  lamina  spiralis 

Inf  undibulum 

Lamina  spiralis 

Vestibular  scale 

Lamina  spiralis 

Tympanic  scale 


Meatus  auditorius  interims 


FIG.  85. 

bone  which  give  rise  to  a  fluted  appearance,  as  shown  in  Fig.  85.  These 
columns  themselves  are  made  up  of  bundles  of  little  tubes,  enclosing  the 
filaments  of  the  auditory  nerve. 

Modiolus. — The  axis  (modiolus)  of  the  cochlea  is  conical.  The  base 
is  at  the  bottom  of  the  mcatus  internus;  the  apex  does  not  extend  beyond 
the  second  turn  of  the  cochlea,  and  joins  the  funnel  formed  by  the  last 
coil.  The  axis  is  composed  of  brittle  and  porous  bone,  and  its  interior 
is  traversed  by  numerous  canals  which  transmit  the  cochlear  nerves  to  the 
lamina  spiralis,  Fig.  86.  One  canal  (canalis  centralis  modioli),  larger 
than  the  rest,  runs  through  the  centre  of  the  axis,  and  opens  on  its  sum- 
mit— that  is,  at  the  apex  of  the  funnel.  It  transmits  a  nerve  to  the  last 
half  turn  of  the  lamina  spiralis. 

The  Meatus  Internus. — The  meatus  auditorius  internus  is  situated 
on  the  posterior  surface  of  the  petrous  bone.  Its  direction  is  nearly  hori- 
zontally outward;  its  length,  about  three-eighths  of  an  inch.  Its  diameter 
varies  a  little  in  different  bones,  but  is  always  larger  than  that  of  the 
nerves  which  it  transmits. 

The  interval  between  the  nerves  and  their  bony  canal  is  occupied  by 


266  HUMAN    OSTEOLOGY. 

the  cerebro-spinal  fluid.  In  fractures  through  the  base  of  the  skull,  in- 
volving the  meatus,  this  fluid  sometimes  oozes  out  through  the  external 
ear.  Whenever  you  observe  this  after  an  injury  to  the  head,  the  case 
must  be  regarded  as  very  grave.  In  thirteen  cases  of  injury  to  the  head 
admitted  into  St.  Bartholomew's  Hospital,  blood  or  watery  fluid  flowed 
from  the  ear.  Of  these  thirteen,  six  died,  and  in  all  six  the  corresponding 


Vestibular  scale  ?  .  .  . 
Lamina  spiralis  .... 
Tympanic  scale  .... 


Cochlear  nerve 


petrous  bone  was  found  fractured.  In  the  seven  cases  that  recovered, 
five  had  bleeding  from  the  ear,  and  two  only  had  a  discharge  of  fluid.  So 
that,  although  a  watery  discharge  be  a  very  unfavorable  symptom,  it  is 
not  necessarily  a  fatal  one. 

By  cutting  away  the  greater  part  of  the  meatus,  as  in  Fig.  87,  the  bot- 
tom of  it  is  found  to  be  divided  by  a  crest  of  bone  into  two  compartments 

tus  Fallopii. 

^  for  the  nerves  to  the  utricle,  the  superior  and  external  semicir- 
r  canals. 
Crest  of  bone. 
Openings  for  the  nerve  to  the  saccule. 


^Opening  of  a  canal  which  transmits  the  nerve  of  the  posterior  semicir- 
cular canal. 

cribrosa,  through  which  the  nerves  pass  to  the  cochlea. 

/ 

X 

Fio.  87.— Foramina  at  the  Bottom  of  the  Right  Meatus  Auditorius  Internus. 

of  unequal  size,  an  upper  and  a  lower.  In  the  upper  and  smaller  one, 
there  are  two  openings,  of  which  the  anterior  is  the  aqueductus  Fallopii 
(transmitting  the  facial  nerve);  the  posterior,  when  examined  with  a  lens, 
presents  a  number  of  minute  foramina  which  transmit  the  divisions  of 
the  vestibular  nerves  which  supply  the  utricle,  the  superior  and  the  ex- 
ternal semicircular  canals. 


THE    ANATOMY    OF    THE    EAR.  2G7 

In  the  lower  and  larger  depression,  we  observe  the  base  of  the  axis  of 
the  cochlea,  termed  '  lamina  cribrosa/  because  it  has  a  double  row  of  fo- 
ramina arranged  spirally,  as  shown  in  the  figure.  Now  take  any  one  of 
these  foramina,  which  appear  scarcely  larger  than  the  point  of  a  pin, 
magnify  it  with  a  lens,  and  you  find  that  it  becomes  a  fossa  pierced  by 
holes  varying  in  number  from  three  to  seven.  So  fine  are  the  canals 
which  transmit  the  filaments  of  the  cochlear  nerve!  In  the  centre  of  the 
lamina  is  the  orifice  of  the  central  canal  of  the  axis,  which  is  the  largest 
of  all.  Behind  the  lamina  are  two  (sometimes  three)  openings  leading 
to  minute  perforations  which  transmit  the  nerve  to  the  'saccule/ 
Lastly,  on  the  posterior  wall  of  the  meatus  is  the  orifice  of  a  very  constant 
canal  (represented  by  the  dotted  outline)  which  gives  passage  to  the  ves- 
tibular  nerve  of  the  posterior  semicircular  canal. 


Ampulla  of  superior  semicircular  canal. 
Ampulla  of  external  semicircular  canal 


Utricle  . 
Saccule. 


Ampulla  of  posterior  semicircular  canal 


FIG.  88.— Membranous  Labyrinth  and  Nerves  of  the  Left  Ear. 

Membranous  Labyrinth. — The  membranous  labyrinth  comprises 
the  two  little  bladders,  termed  the  *  utricle '  and  the  *  saccule/  in  the  ves- 
tibule, and  the  membranous  semicircular  canals  together  with  part  of  the 
cochlea.  It  floats  in  the  perilymph,  and  contains  the  endolymph.  It  is 
partly  represented  in  Fig.  88. 

Utricle. — The  utricle  occupies  the  upper  half  of  the  vestibule.  It  is 
very  difficult  to  make  a  good  display  of  it.  The  best  way  to  examine  it, 
is  to  remove  very  carefully  the  roof  of  the  vestibule  and  that  of  the  supe- 
rior semicircular  canal,  and  then  to  put  the  preparation  into  water.  All 
the  membranous  semicircular  canals  open  into  it.  It  floats  free  in  the 
perilymph  except  at  its  fossa,  the  '  fovea  hemielliptica/ where  it  is  retained 
against  the  sieve-like  plate  of  bone  through  which  the  utricular  nerves 
enter.  The  utricle  sends  a  slender  canal  down  the  aqueductus  vestibuli, 
which  ends  in  a  blind  extremity  outside  that  aqueduct  at  the  back  of 
the  petrous  part  of  the  temporal  bone.  This  canal  is  joined,  close  to  its 


268  HUMAN"    OSTEOLOGY. 

origin,  by  another  from  the  saccule.  Thus  the  utricle  and  saccule  do 
communicate,  though  indirectly. 

Saccule. — The  saccule  is  smaller  than  the  utricle  and  situated  below 
it,  close  to  its  appropriate  fossa,  the  '  fovea  hemispherical  It  is  attached 
to  this  fossa  by  the  saccular  nerve  in  the  same  way  as  the  utricle  is  attached 
by  nerve  filaments  to  the  fovea  hemielliptica.  The  saccule  is  connected 
with  the  membranous  canal  of  the  cochlea  by  a  small  duct,  the  '  canalis 
uniens/  The  utricle  communicates  with  the  saccule  in  the  indirect 
manner  just  described.  Hence  the  different  parts  of  the  membranous 
labyrinth  communicate  throughout,  like  the  same  parts  in  the  bony 
labyrinth. 

Otoliths. — On  the  inner  wall  of  the  utricle  and  saccule,  at  the  spot 
where  the  nerves  spread  out  upon  them,  is  a  small  mass  of  crystals  of 
carbonate  of  lime.  The  two  masses  are  the  'otoconia'  or  'otoliths/  and 
are  homologues  of  the  large  white  '  ear-stones '  seen  in  the  cod  and  whit- 
ing, and  found  in  most  of  the  osseous  fishes.110 

Membranous  Semicircular  Canals.— The  membranous  semicir- 
cular canals,  except  at  their  ampullae,  fill  only  about  one-third  the  space 
of  the  bony  canals;  the  remainder  is  occupied  by  the  perilymph.  The 
nerve  destined  to  each  membranous  ampulla  spreads  out  only  on  that 
surface  of  the  ampulla  which  is  toward  the  convexity  of  the  rest  of  the 
canal.  The  nerve  does  not  advance  beyond  the  ampulla,  but  ramifies  on 
a  crescent-shaped  septum  (septum  transversum)  which  projects  into  the 
interior. 

Membranous  Cochlea. — The  membranous  cochlea  forms  a  third 
scale,  the  '  scala  media '  or  '  canalis '  or  '  ductus  cochlearis '  (Fig.  89), 
separating  the  scala  vestibuli  from  the  scala  tympani.  Its  floor  is  at- 
tached to  the  margin  of  the  bony  lamina  spiralis  (L.  Sp.  0.  V.,  L.  Sp. 
O.  T.)  and  reaches  across  to  the  outer  wall  of  the  cochlea,  to  which  it  is 
attached  by  a  process  of  periosteum,  the  'ligamentum  spirale'  (L.  Sp.). 
This  floor  is  named  '  membrana  basilaris/  or  '  membranous  lamina  spiralis.' 
The  roof  is  a  very  delicate  membranous  lamina,  the  '  membrane  of 
Reissner';  it  is  turned  toward  the  vestibular  scale.  Hence  the  'scala 

110  For  details  concerning  the  minute  structure  of  the  vestibule  and  the  connec- 
tion of  the  otoliths  with  certain  hair-like  bodies  belonging  to  the  nerve-filaments,  see 
Dr. Urban  Pritchard's  paper  on  '  The  Termination  of  the  Nerves  in  the  Vestibule  and 
Semicircular  Canals  of  Mammals. '— '  Quarterly  Journal  of  Microscopic  Science, ' 
October  1876. 


THE    ANATOMY    OF   THE    EAR. 


269 


media '  is  bounded  by  the  '  membrana  basilaris/  '  the  membrane  of  Riess- 
ner ' ;  and  the  segment  of  the  outer  wall  of  the  cochlea  included  between 
the  outer  attachments  of  these  two  membranes.  This  '  canalis  cochlearis ' 
communicates  at  one  end  with  the  saccule  by  the  '  canalis  uniens,'  so  that 
the  endolymph  is  continuous  in  both  those  cavities;  at  the  other  end, 
toward  the  apex  of  the  cochlea,  it  terminates  in  a  blind  extremity  fixed 
to  the  wall  of  the  cupola,  partly  bounding  the  helicotrema* 


FIG.  89.— Vertical  Section  of  the  First  Turn  of  the  Cochlea,  showing  the  Membranous  Cochlea  and  the 
Position  of  the  Organ  of  Corti.    After  Waldeyer  and  Quain. 

Organ  of  Corti. — In  this  '  canalis  cochlearis/  resting  on  the  '  mem- 
brana basilaris/  are  two  rows  of  cells  (Fig.  89  O.C.),  an  outer  and  an 
inner,  leaning  toward  each  other,  so  that  there  is  a  tunnel  (T.C.)  formed 
between  them.  They  are  covered,  but  only  partially,  by  a  membrane 
(membrana  tectoria)  attached  to  the  edge  of  the  bony  lamina  spiralis. 
Their  singular  characters  and  very  complicated  appendages  are  subjects 
too  minute  to  be  described  here.111 

111  Corti's  ori<rinal  paper  in  Siebold  and  KSlliker's  '  Zeitsch.  f.  Wissensch.  Zoolo- 
gie,' vol.  iii. 


270  HUMAN    OSTEOLOGY. 

Probable  Use  of  the  Organ  of  Corti. — This  organ  is  arranged 
on  the  principle  of  the  chords  or  notes  of  a  musical  instrument,  so  that 
different  sets  of  certain  fine  appendages  to  its  cells  may  vibrate  in  accord- 
ance with  different  kinds  of  vibrations  transmitted  from  without  to  the 
labyrinth.  As  they  communicate  with  nerves  these  differences  can  thus 
make  an  impression  on  the  brain.  Hence,  by  means  of  the  organ  of  Corti, 
we  can  distinguish  musical  notes  and  the  refinements  of  tone  in  delicate 
sounds,  the  remaining  portions  of  the  labyrinth  being  sufficient  for  ordi- 
nary hearing. 


INDEX. 


ACETABULUM,  144 

Acromion,  205 

Air  cells  in  bone,  7 

Alveolar  process,  71 

Ampullae,  254 

Analysis  of  bones,  3 

Anatomical  neck  of  humerus,  20' 

Animal  matter  of  bone,  3 

Anterior  clinoid  process,  60 

Antlers,  47 

Antrum  of  Highmore,  58 

Aquaeductus  cochleae,  52 

Fallopii,  260 

vestibuli.  52 
Arch,  carpal,  225 

of  foot,  167 
Arches  of  foot,  181 
Articular  arteries,  9 
Arytenoid  cartilages,  245 
Astragalus,  168 
Atlas,  119 
Axis,  120 

BASILAR  process,  33,  102 
Bicipital  groove  of  humerus,  211 
Blood  supply  of  bones,  9 
Bones,  air  cells  in,  7 

classification  of,  5 

composition  of,  2 

elasticity  of,  5 

hollow  shaft  of,  6 

microscopic  structure  of,  12 

naked  eye  structure  of,  6 


Bones,  nomenclature  of,  6 
properties  of,  4 
strength  of,  5 
uses  of,  1 

CALCANEUM,  171 

Callus,  32 

Callus  provisional,  32 

Canals,  accessory  palatine,  82 

Canal,  anterior  dental,  69 

anterior  palatine,  74,  99 

carotid,  54,  259 

infra-orbital,  69 

of  Huguier,  49,  258 

posterior  palatine,  69,  81 

pterygo-palatine,  100 

malar,  77 

semicircular,  254,  264 

membranous,  268 

vertebral,  129 

Vidian,  62 

Canaliculi  of  bone,  13 
Canalis  centralis  modioli,  265 
Cancellous  tissue,  8 
Canine  fossa,  69 
Carotid  canal,  259  , 

Carpal  arch,  225 
Carpus,  224 
Cartilages,  costal,  192 
Cavity,  sigmoid.  of  radius,  218 

of  ulna,  219 
Cells,  ethmoidal,  64 

frontal,  41 


272 


INDEX. 


Cells,  mastoid,  49 

maxillary,  70 

palatine,  82 

sphenoidal,  58 
Clavicle,  202 

curves  of,  202 
Coccyx,  136 
Cochlea,  253,  264 

membranous,  268 

Condyloid  ridge  of  humerus,  external, 
212 

internal,  212 
Coracoid  process,  ?07 
Cords,  vocal,  246 
Cornua  spenoidalia,  58 
Coronoid  fossa,  213 

process  of  lower  jaw,  88 

ulna,  219 

Corti,  organ  of,  254,  269 
Costal  cartilages,  192 
Cranial  fossae,  97 
Cribriform  plate,  64 
Cricoid  cartilage,  244 
Crista  galli,  64 

vestibuli,  263 
Cuboid  bone,  174 
Cuneiform  bone  of  carpus,  227 

bones  of  tarsus,  175 

cartilages  of  larynx,  246 
Cupola,  265 
Cuvier  on  fossil  bones,  115 

DENTAL  foramen,  88 
Digital  fossa,  154 
Diploe,  10,  89 
Diploic  veins,  10 
Ductus  cochlearis,  268 

EAR,  anatomy  of,  252 
Earthy  matter  of  bones,  3 
Endosteum,  11 
Ensiform  cartilage,  187 
Epiglottis,  245 


Epipteric  bone,  55 
Ethmoid  bone,  64 
Ethmoidal  foramen,  anterior,  65 
posterior,  66 
notch,  45 
Eustachian  tube,  51,  252 

FACE,  bones  of,  68 
Facial  angle,  112 
Falx  cerebri,  64 
Femur,  151 
Fenestra  ovalis,  253,  258 

rotunda,  253,  258 
Fibula,  163 
First  rib,  191 
Fissura  Glaseri,  49 
Fissure,  Glaserian,  258 

sphenoidal,  60,  106 

spheno-maxillary,  106 
Floating  ribs,  189 
Fontanelles,  39 
Foot,  arches  of,  167 

as  a  whole,  181 

bones  of,  167 

lever  of  second  order,  168 

mechanism  in  walking,  183 
Foramen  caecum,  44 

chordae,  258 

condyloid,  anterior,  103 
posterior,  103 

ethmoidal,  anterior,  65 
posterior,  65 

infra-orbital,  69 

magnum,  33 

mentale,  89 

obturatum,  143 

occipital,  103 

opticum,  60 

ovale,  143 

parietal,  94 

rotundum,  61 

spheno -palatine,  82 

spinosum,  61 


INDEX. 


273 


Foramen  stylo- mastoid,  53 

supra-orbital,  43 

Vesalii,  61 
Fossa,  canine,  69 

coronoid,  213 

digastric,  50 

digital,  154 

iliac,  139 

jugular,  53 

mental,  86 

olecranon,  213 

pituitary,  57 

pterygoid,  61 

scaphoid,  61 

spheno-maxillary,  104 

temporal,  94 

zygomatic,  103 
Fossae,  nasal,  107 

of  skull,  107 
Fovea  hemielliptica,  263 

hemispherica,  263 
Fractures,  repair  of,  31 
Frontal  bone,  41 

sinus,  41 

GLASERIAN  fissure,  258 

Glenoid  cavity,  48,  206 

Glenoid  fissure,  49 

Glottis,  248 

Groove,  bicipital,  of  humerus,  211 

optic,  57 

Growth  in  length  of  bones,  30 
Gumboil,  72 

HAMULAR  process,  61 
Hamulus  of  cochlea,  265 
Hamulus  of  lachrymal  bone,  80 
Hand,  bones  of,  224 
Haversian  canals,  12, 15,  30 

interspaces,  13 

lamellae,  13 

system,  13 
Helicotrema,  265 

Herodotus  on  Egyptian  embalming,  107 
Hiatus  Fallopii,  51 


Highmore,  antrum  of,  68 

Hollow  shaft  of  bone,  6 

Horns,  47 

Huguier,  canal  of,  258 

Humerus,  209 

Hunter's  experiments  with  shots,  30 

Hyoid  bone,  241 

INCUS,  252,  261 
Inferior  maxillary  bone,  86 
Inferior  spongy  bone,  84 
turbinated  bone,  84 
Infra-orbital  canal,  69 

foramen,  69 
Infundibulum,  41,  66 
Iliac  fossa,  139 
Ilium,  139 

Innominate  bone,  138 
Insertion  of  muscles,  34 
Inspiration,  mechanism  of,  193 
Intervertebral  fibro-cartilage,  127 
Ischium,  143 

JAW,  buttresses  of  upper,  112 
Jaw,  joint  of,  90 
Jaw-bone,  lower,  86 
upper,  68 
Jugular  foramen,  102 

fossa,  53 

LABYRINTH  membranous,  267 
Lachrymal  bone,  80 
Lachrymal  fossa,  45 

groove,  73,  80 

process,  84 

sac,  73 

Lacunae  of  bone,  13 
Lamina  cribrosa  cochlea?,  267 

spiralis  ossea,  253,  205 
Larynx,  243 
Layers  of  bone,  7 
Levers,  bones  act  as,  2 
Linea  aspera,  154 
Lower  extremity,  bones  of,  188 
Lymphatics  of  bone,  12 

MADDER,  experiments  with,  28 


274 


INDEX. 


Malar  bone,  77 

canals,  77 

Malleolus  externus,  164 
internus,  162 
Malleus,  252,  261 
Manubrium,  187 
Marrow,  artery  of,  10 

red.  9 

yellow,  9 

Mastoid  process,  49 
Maxillary  sinus,  70 
Meatus  auditorius  externus,  50,  255 

internus,  51,  265 

of  nose,  66,  108 

Median  crest  of  palate  bone,  81 
Medullary  artery,  10 

membrane,  11 

Membrana  tympani,  252,  257 
Metacarpus,  229 
Metatarsus,  177 

Microscopic  structure  of  bone,  12 
Milk  dentition,  71 
Modiolus,  265 
Muscles  in  front  of  the  spine,  201 

of  back,  198 

superficial,  198 

of  the  back  of  the  neck,  200 
Myeloid  cells,  9 
NASAL  bone,  78 
Nasal  duct,  73 
Nasal  fossae,  107 

process  of  sup.  maxillary  bone,  73 

slit,  65 

spine,  anterior,  74 
posterior,  81 

suture,  79 
Neck  of  humerus,  anatomical,  209 

surgical,  211 
Necrosis,  31 
Nerves  in  bone,  11 
Neuralgia  of  bone,  11 
Nose,  meatus  of,  108 

posterior  openings  of,  100 

septum  of,  109 


Notch  of  acetabulum,  144 
intercondyloid,  155 
ischiatic,  greater,  140 

lesser,  140 
sigmoid,  219 
Notches  in  sternum,  187 
Nutrient  artery  of  bone,  10* 

OCCIPITAL  bone,  33 
Olecranon,  220 
Olecranon  fossa,  213 
Optic  foramen,  60 

groove,  57 

Orbital  wings  of  sphenoid,  60 
Orbits,  104 
Organ  of  Corti,  269 
Origin  of  muscles,  34 
Os  calcis,  171 
Os  hyoides,  241 
Os  innominatum,  138 
Os  magnum,  228 
Os  orbiculare,  261 
Os  planum,  65 
Os  unguis,  80 
Ossa  triquetra,  93 
Ossification,  30 
Osteoblasts,  31 
Osteology,  interest  of,  1 
Otoliths,  268 

PACCHIONIAN  bodies,  39,  94 
Palate  bone,  81 
Parietal  bone,  38 
Paroccipital  process,  37 
Patella,  158 
Pelvis,  arch  of,  147 

axes  of,  148 

brim  of  the,  139 

diameters  of,  148 

lever  of  first  order,  146 

obliquity  of,  148 

sexual  differences  of,  149 
Periosteum,  11 

blood-vessels  of,  11 

value  of,  30 


INDEX. 


275 


Perivascular  lymphatics,  12 
Phalanges  of  fingers,  233 

of  toes,  180 
Phosphate  of  lime,  4 
Pisiform  bone,  227 
Pituitary  fossa,  57 
Pre-maxillary  bones,  75 

suture,  75 
Process,  acromion,  205 

alveolar,  71 

basilar,  102 

clinoid,  57 

coracoid,  207 

coronoid,  of  lower  jaw,  88 
of  ulna,  219 

hamular,  61 

lachrymal,  84 

malar,  74 

mast  oid,  49 

nasal,  73 

palatine,  73 

post  glenoid,  49 

pterygoid,  61,  100 

sphenoidal,  83 

styloid,  53 

of  radius,  218 
of  ulna,  222 

unciform,  66 

vaginal,  59 

Promontory  of  tympanum,  258 
Pterygoid  process,  61 
Pterygo-palatine  canal,  59 
Pubes,  141 
Pyramid,  258 

RADIUS,  216 

Radius,  rotation  of,  216 

Repair  of  fractures,  31 

Ribs,  general  characters  of,  189 

Rickety  bones,  3 

Ridge,  deltoid,  211 

gluteal,  155 
Ridges,  intertrochanteric,  154 

condyloid  of  humerus,  212 
Rima  clottidis.  24* 


Rostrum  of  sphenoid,  58 

SABRE  cuts,  30 

Saccule,  268 

Sacro-iliac  symphysis,  135,  140 

Sacrum,  132 

Santorini,  cartilages  of,  245 

Scala  tympani,  254 

vestibuli,  254 

Scaphoid  bone  of  carpus,  226 
of  tarsus,  173 

fossa,  61 
Scapula,  205 

spine  of,  205 
Sella  Turcica,  57,  60 
Semicircular  canals,  254,  264 

membranous,  268 
Semilunar  bone,  227 
Septum  of  nose,  109 
Sesamoid  bones  of  hand,  235 
of  foot,  180 

Sigmoid  cavity  of  radius,  218 
Sinus,  frontal,  41 

inferior  petrosal,  98 

lateral,  98 

superior  petrosal,  98 
Skeleton,  general  survey  of,  237 
Skull  as  a  whole,  92 

base  of,  97 

bones  of,  33 

buttresses  of,  111 

-cap,  94 

general  observations  on,  109 

lever  of  first  order,  109 

locking  of  bones  of,  110 

power  of  resisting  shocks,  111 

sexual  differences,  112 

tables  of,  109 
Sphenoid  bone,  56 

lesser  wings  of,  60 

rostrum  of,  58 
Sphenoidal  fissure,  106 

process,  83 
Spheno-maxillary  fossa,  104 

fissure.  106 


276 


IXDEX. 


Spheno-palatine  foramen,  83 
Spine,  116 

curves  of,  126 

ethmoidal,  56 

extent  of  motion  of,  126 

of  pubes,  143 

of  scapula,  203 
Spines  of  ilium,  anterior  and  posterior, 

140 

Spongy  bones,  66 
Squamosal  bone,  47 
Stapes,  252,  261 
Stature  of  individual,  30 
Sternum,  186 
Styloid  process  of  radius,  218 

of  ulna,  222 
Superciliary  ridge,  41 
Superior  maxillary  bone,  68 
Surgical  neck  of  humerus,  211 
Suture,  basilar,  57 
coronal,  45 

zygomatic,  55 
Sutures  of  skull,  92 
Symphysis  of  lower  jaw,  86 

pubis,  142 

sacro-iliac,  135,  140 

TABLES  of  skull,  109 
Tarsus,  bones  of,  167 
Tarsus,  tunnel  of,  170 
Teeth,  71 

fangs  of,  72 

milk,  71 

of  lower  jaw,  87 

of  upper  jaw,  72 

permanent,  72 

sockets  of,  72 
Temporal  bone,  47 

mastoid  portion  of,  49 
petrous  portion  of,  50 
squamous  portion  of,  47 
Tendo  oculi,  73 
Thorax  as  a  whole,  193 

general  description  of,  186 
Thyroid  cartilage,  243 


Tibia,  159 

Toes,  relative  length  of,  183 

Torcular  Herophili,  36 

Trapezium,  228 

Trochanters,  major  and  minor,  153 

Tubercle  of  radius,  216 

Tubercles  of  dorsal  and  lumbar  verte- 
bra, 124 

Tuberosities  of  femur,  157 
of  humerus,  greater,  210 

lesser,  210 
of  tibia,  160 

Tuberosity  of  ischium,  144 

Tunnel  of  tarsus,  170 

Turbinated  bones,  66 
bone,  spheuoidal,  58 

Tympanum,  252 

ULNA,  219 

Unciform  bone,  228 
Unciform  process,  66 
Upper  extremity,  bones  of,  202 
Utricle,  267 

VAGINAL  processes,  59 
Ventricles  of  larynx,  24? 
Vertebra,  constituent  parts  of,  116 
Vertebrae,  cervical,  118 

coccygeal,  136 

dorsal,  122 

lumbar,  123 

sacral,  133 
Vertebral  canal,  129 

column,  116, 126 

shape  of,  128 
strength  of,  126 

groove,  129 
Vestibule,  253,  263 
Vidian  canal,  61 
Vocal  cords,  246 
Vomer,  85 

WALKING,  mechanism  of  foot  in,  183 
"Wormian  bones,  93 

ZYGOMA,  48 
Zygomatic  fossa,  103 


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